Imported from libpng-0.99d.tar
diff --git a/CHANGES b/CHANGES
index cffbe93..20bca9b 100644
--- a/CHANGES
+++ b/CHANGES
@@ -223,5 +223,13 @@
version 0.99c [February 7, 1998]
More type casting. Removed erroneous overflow test in pngmem.c.
Added png_buffered_memcpy() and png_buffered_memset(), apply them to rowbytes.
- Added UNIX manual pages libpng.3, initially created by R. P. C. Rodgers,
- U.S. National Library of Medicine (rodgers@nlm.nih.gov), and png.5.
+ Added UNIX manual pages libpng.3 (incorporating libpng.txt) and png.5.
+version 0.99d [February 8, 1998]
+ Renamed "far_to_near()" "png_far_to_near()"
+ Revised libpng.3
+ Version 99c "buffered" operations didn't work as intended. Replaced them
+ with png_memcpy_check() and png_memset_check().
+version 0.99e [February 9, 1998]
+ Fixed a bug with background compositing of paletted images in pngrtran.c
+ Added many "if (png_ptr == NULL) return" to quell compiler warnings about
+ unused png_ptr, mostly in pngget.c and pngset.c.
diff --git a/README b/README
index 223cc56..c5e9161 100644
--- a/README
+++ b/README
@@ -1,4 +1,4 @@
-[NOTE: this is still beta version 0.99c; the text below has already
+[NOTE: this is still beta version 0.99d; the text below has already
been updated in anticipation of the imminent 1.0 release.]
diff --git a/libpng.3 b/libpng.3
index 34bbda8..398f49b 100644
--- a/libpng.3
+++ b/libpng.3
@@ -1,10 +1,700 @@
-.TH PNG 5 "February 7, 1998"
+.TH PNG 5 "February 8, 1998"
.SH NAME
libpng \- Portable Network Graphics (PNG) format
.SH SYNOPSIS
-[see
-.I png.h
-for full description]
+
+#include <png.h>
+
+
+void png_build_gamma_table (png_structp png_ptr);
+
+void png_build_grayscale_palette (int bit_depth, png_colorp
+palette);
+
+void png_calculate_crc (png_structp png_ptr, png_bytep ptr,
+png_size_t length);
+
+void png_check_chunk_name (png_structp png_ptr, png_bytep
+chunk_name);
+
+png_size_t png_check_keyword (png_structp png_ptr, png_charp
+key, png_charpp new_key);
+
+int png_check_sig (png_bytep sig, int num);
+
+void png_chunk_error (png_structp png_ptr, png_const_charp
+error);
+
+void png_chunk_warning (png_structp png_ptr, png_const_charp
+message);
+
+void png_combine_row (png_structp png_ptr, png_bytep row, int
+mask);
+
+void png_convert_from_struct_tm (png_timep ptime, struct tm FAR
+* ttime);
+
+void png_convert_from_time_t (png_timep ptime, time_t ttime);
+
+png_charp png_convert_to_rfc1123 (png_structp png_ptr,
+png_timep ptime);
+
+void png_correct_palette (png_structp png_ptr, png_colorp
+palette, int num_palette);
+
+int png_crc_error (png_structp png_ptr);
+
+int png_crc_finish (png_structp png_ptr, png_uint_32 skip);
+
+void png_crc_read (png_structp png_ptr, png_bytep buf,
+png_size_t length);
+
+png_infop png_create_info_struct (png_structp png_ptr);
+
+png_structp png_create_read_struct (png_const_charp
+user_png_ver, voidp error_ptr, png_error_ptr error_fn,
+png_error_ptr warn_fn);
+
+png_voidp png_create_struct (int type);
+
+png_structp png_create_write_struct (png_const_charp
+user_png_ver, voidp error_ptr, png_error_ptr error_fn,
+png_error_ptr warn_fn);
+
+void png_debug_free (png_structp png_ptr, png_voidp ptr);
+
+png_voidp png_debug_malloc (png_structp png_ptr, png_uint_32
+size);
+
+void png_destroy_info_struct (png_structp png_ptr, png_infopp
+info_ptr_ptr);
+
+void png_destroy_read_struct (png_structpp png_ptr_ptr,
+png_infopp info_ptr_ptr, png_infopp end_info_ptr_ptr);
+
+void png_destroy_struct (png_voidp struct_ptr);
+
+void png_destroy_write_struct (png_structpp png_ptr_ptr,
+png_infopp info_ptr_ptr);
+
+void png_do_background (png_row_infop row_info, png_bytep row,
+png_color_16p trans_values, png_color_16p background,
+png_color_16p background_1, png_bytep gamma_table, png_bytep
+gamma_from_1, png_bytep gamma_to_1, png_uint_16pp gamma_16,
+png_uint_16pp gamma_16_from_1, png_uint_16pp gamma_16_to_1, int
+gamma_shift);
+
+void png_do_bgr (png_row_infop row_info, png_bytep row);
+
+void png_do_chop (png_row_infop row_info, png_bytep row);
+
+void png_do_dither (png_row_infop row_info, png_bytep row,
+png_bytep palette_lookup, png_bytep dither_lookup);
+
+void png_do_expand (png_row_infop row_info, png_bytep row,
+png_color_16p trans_value);
+
+void png_do_expand_palette (png_row_infop row_info, png_bytep
+row, png_colorp palette, png_bytep trans, int num_trans);
+
+void png_do_gamma (png_row_infop row_info, png_bytep row,
+png_bytep gamma_table, png_uint_16pp gamma_16_table, int
+gamma_shift);
+
+void png_do_gray_to_rgb (png_row_infop row_info, png_bytep
+row);
+
+void png_do_invert (png_row_infop row_info, png_bytep row);
+
+void png_do_pack (png_row_infop row_info, png_bytep row,
+png_uint_32 bit_depth);
+
+void png_do_packswap (png_row_infop row_info, png_bytep row);
+
+void png_do_read_filler (png_row_infop row_info, png_bytep row,
+png_uint_32 filler, png_uint_32 flags);
+
+void png_do_read_interlace (png_row_infop row_info, png_bytep
+row, int pass, png_uint_32 transformations);
+
+void png_do_read_invert_alpha (png_row_infop row_info,
+png_bytep row);
+
+void png_do_read_swap_alpha (png_row_infop row_info, png_bytep
+row);
+
+void png_do_read_transformations (png_structp png_ptr);
+
+void png_do_rgb_to_gray (png_row_infop row_info, png_bytep
+row);
+
+void png_do_shift (png_row_infop row_info, png_bytep row,
+png_color_8p bit_depth);
+
+void png_do_strip_filler (png_row_infop row_info, png_bytep
+row, png_uint_32 flags);
+
+void png_do_swap (png_row_infop row_info, png_bytep row);
+
+void png_do_unpack (png_row_infop row_info, png_bytep row);
+
+void png_do_unshift (png_row_infop row_info, png_bytep row,
+png_color_8p sig_bits);
+
+void png_do_write_interlace (png_row_infop row_info, png_bytep
+row, int pass);
+
+void png_do_write_invert_alpha (png_row_infop row_info,
+png_bytep row);
+
+void png_do_write_swap_alpha (png_row_infop row_info, png_bytep
+row);
+
+void png_do_write_transformations (png_structp png_ptr);
+
+void png_error (png_structp png_ptr, png_const_charp error);
+
+void *png_far_to_near (png_structp png_ptr,png_voidp ptr,
+int check);
+
+void png_flush (png_structp png_ptr);
+
+void png_free (png_structp png_ptr, png_voidp ptr);
+
+png_byte png_get_bit_depth (png_structp png_ptr, png_infop
+info_ptr);
+
+png_uint_32 png_get_bKGD (png_structp png_ptr, png_infop
+info_ptr, png_color_16p *background);
+
+png_byte png_get_channels (png_structp png_ptr, png_infop
+info_ptr);
+
+png_uint_32 png_get_cHRM (png_structp png_ptr, png_infop
+info_ptr, double *white_x, double *white_y, double *red_x,
+double *red_y, double *green_x, double *green_y, double
+*blue_x, double *blue_y);
+
+png_byte png_get_color_type (png_structp png_ptr, png_infop
+info_ptr);
+
+png_byte png_get_compression_type (png_structp png_ptr,
+png_infop info_ptr);
+
+png_voidp png_get_error_ptr (png_structp png_ptr);
+
+png_byte png_get_filter_type (png_structp png_ptr, png_infop
+info_ptr);
+
+png_uint_32 png_get_gAMA (png_structp png_ptr, png_infop
+info_ptr, double *file_gamma);
+
+png_uint_32 png_get_hIST (png_structp png_ptr, png_infop
+info_ptr, png_uint_16p *hist);
+
+png_uint_32 png_get_image_height (png_structp png_ptr,
+png_infop info_ptr);
+
+png_uint_32 png_get_image_width (png_structp png_ptr, png_infop
+info_ptr);
+
+png_int_32 png_get_int_32 (png_bytep buf);
+
+png_byte png_get_interlace_type (png_structp png_ptr, png_infop
+info_ptr);
+
+png_voidp png_get_io_ptr (png_structp png_ptr);
+
+png_uint_32 png_get_IHDR (png_structp png_ptr, png_infop
+info_ptr, png_uint_32 *width, png_uint_32 *height, int
+*bit_depth, int *color_type, int *interlace_type, int
+*compression_type, int *filter_type);
+
+png_uint_32 png_get_oFFs (png_structp png_ptr, png_infop
+info_ptr, png_uint_32 *offset_x, png_uint_32 *offset_y, int
+*unit_type);
+
+png_uint_32 png_get_pCAL (png_structp png_ptr, png_infop
+info_ptr, png_charp *purpose, png_int_32 *X0, png_int_32 *X1,
+int *type, int *nparams, png_charp *units, png_charpp *params);
+
+png_uint_32 png_get_pHYs (png_structp png_ptr, png_infop
+info_ptr, png_uint_32 *res_x, png_uint_32 *res_y, int
+*unit_type);
+
+float png_get_pixel_aspect_ratio (png_structp png_ptr,
+png_infop info_ptr);
+
+png_uint_32 png_get_pixels_per_meter (png_structp png_ptr,
+png_infop info_ptr);
+
+png_voidp png_get_progressive_ptr (png_structp png_ptr);
+
+png_uint_32 png_get_PLTE (png_structp png_ptr, png_infop
+info_ptr, png_colorp *palette, int *num_palette);
+
+png_uint_32 png_get_rowbytes (png_structp png_ptr, png_infop
+info_ptr);
+
+png_uint_32 png_get_sBIT (png_structp png_ptr, png_infop
+info_ptr, png_color_8p *sig_bit);
+
+png_bytep png_get_signature (png_structp png_ptr, png_infop
+info_ptr);
+
+png_uint_32 png_get_sRGB (png_structp png_ptr, png_infop
+info_ptr, int *intent);
+
+png_uint_32 png_get_text (png_structp png_ptr, png_infop
+info_ptr, png_textp *text_ptr, int *num_text);
+
+png_uint_32 png_get_tIME (png_structp png_ptr, png_infop
+info_ptr, png_timep *mod_time);
+
+png_uint_32 png_get_tRNS (png_structp png_ptr, png_infop
+info_ptr, png_bytep *trans, int *num_trans, png_color_16p
+*trans_values);
+
+png_uint_16 png_get_uint_16 (png_bytep buf);
+
+png_uint_32 png_get_uint_32 (png_bytep buf);
+
+png_uint_32 png_get_valid (png_structp png_ptr, png_infop
+info_ptr, png_uint_32 flag);
+
+png_uint_32 png_get_x_offset_microns (png_structp png_ptr,
+png_infop info_ptr);
+
+png_uint_32 png_get_x_offset_pixels (png_structp png_ptr,
+png_infop info_ptr);
+
+png_uint_32 png_get_y_offset_microns (png_structp png_ptr,
+png_infop info_ptr);
+
+png_uint_32 png_get_y_offset_pixels (png_structp png_ptr,
+png_infop info_ptr);
+
+void png_handle_bKGD (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 length);
+
+void png_handle_cHRM (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 length);
+
+void png_handle_gAMA (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 length);
+
+void png_handle_hIST (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 length);
+
+void png_handle_IEND (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 length);
+
+void png_handle_IHDR (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 length);
+
+void png_handle_oFFs (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 length);
+
+void png_handle_pCAL (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 length);
+
+void png_handle_pHYs (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 length);
+
+void png_handle_PLTE (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 length);
+
+void png_handle_sBIT (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 length);
+
+void png_handle_sRGB (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 length);
+
+void png_handle_tEXt (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 length);
+
+void png_handle_tIME (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 length);
+
+void png_handle_tRNS (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 length);
+
+void png_handle_unknown (png_structp png_ptr, png_infop
+info_ptr, png_uint_32 length);
+
+void png_handle_zTXt (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 length);
+
+void png_info_destroy (png_structp png_ptr, png_infop
+info_ptr);
+
+void png_info_init (png_infop info_ptr);
+
+void png_init_io (png_structp png_ptr, FILE *fp);
+
+void png_init_read_transformations (png_structp png_ptr);
+
+png_voidp png_malloc (png_structp png_ptr, png_uint_32 size);
+
+voidp png_memcpy (png_voidp s1, png_voidp s2, png_size_t size);
+
+png_voidp png_memcpy_check (png_structp png_ptr, png_voidp s1,
+png_voidp s2, png_uint_32 size);
+
+voidp png_memset (png_voidp s1, int value, png_size_t size);
+
+png_voidp png_memset_check (png_structp png_ptr, png_voidp
+s1, int value, png_uint_32 size);
+
+void png_process_data (png_structp png_ptr, png_infop info_ptr,
+png_bytep buffer, png_size_t buffer_size);
+
+void png_process_IDAT_data (png_structp png_ptr, png_bytep
+buffer, png_size_t buffer_length);
+
+void png_process_some_data (png_structp png_ptr, png_infop
+info_ptr);
+
+void png_progressive_combine_row (png_structp png_ptr,
+png_bytep old_row, png_bytep new_row);
+
+void png_push_check_crc (png_structp png_ptr);
+
+void png_push_crc_finish (png_structp png_ptr);
+
+void png_push_crc_skip (png_structp png_ptr, png_uint_32
+length);
+
+void png_push_fill_buffer (png_structp png_ptr, png_bytep
+buffer, png_size_t length);
+
+void png_push_handle_tEXt (png_structp png_ptr, png_infop
+info_ptr, png_uint_32 length);
+
+void png_push_handle_unknown (png_structp png_ptr, png_infop
+info_ptr, png_uint_32 length);
+
+void png_push_handle_zTXt (png_structp png_ptr, png_infop
+info_ptr, png_uint_32 length);
+
+void png_push_have_end (png_structp png_ptr, png_infop
+info_ptr);
+
+void png_push_have_info (png_structp png_ptr, png_infop
+info_ptr);
+
+void png_push_have_row (png_structp png_ptr, png_bytep row);
+
+void png_push_process_row (png_structp png_ptr);
+
+void png_push_read_chunk (png_structp png_ptr, png_infop
+info_ptr);
+
+void png_push_read_end (png_structp png_ptr, png_infop
+info_ptr);
+
+void png_push_read_IDAT (png_structp png_ptr);
+
+void png_push_read_sig (png_structp png_ptr, png_infop
+info_ptr);
+
+void png_push_read_tEXt (png_structp png_ptr, png_infop
+info_ptr);
+
+void png_push_read_zTXt (png_structp png_ptr, png_infop
+info_ptr);
+
+void png_push_restore_buffer (png_structp png_ptr, png_bytep
+buffer, png_size_t buffer_length);
+
+void png_push_save_buffer (png_structp png_ptr);
+
+void png_read_data (png_structp png_ptr, png_bytep data,
+png_size_t length);
+
+void png_read_destroy (png_structp png_ptr, png_infop info_ptr,
+png_infop end_info_ptr);
+
+void png_read_end (png_structp png_ptr, png_infop info_ptr);
+
+void png_read_filter_row (png_structp png_ptr, png_row_infop
+row_info, png_bytep row, png_bytep prev_row, int filter);
+
+void png_read_finish_row (png_structp png_ptr);
+
+void png_read_image (png_structp png_ptr, png_bytepp image);
+
+void png_read_info (png_structp png_ptr, png_infop info_ptr);
+
+void png_read_init (png_structp png_ptr);
+
+void png_read_push_finish_row (png_structp png_ptr);
+
+void png_read_row (png_structp png_ptr, png_bytep row,
+png_bytep display_row);
+
+void png_read_rows (png_structp png_ptr, png_bytepp row,
+png_bytepp display_row, png_uint_32 num_rows);
+
+void png_read_start_row (png_structp png_ptr);
+
+void png_read_transform_info (png_structp png_ptr, png_infop
+info_ptr);
+
+void png_read_update_info (png_structp png_ptr, png_infop
+info_ptr);
+
+void png_reset_crc (png_structp png_ptr);
+
+void png_save_int_32 (png_bytep buf, png_int_32 i);
+
+void png_save_uint_16 (png_bytep buf, unsigned int i);
+
+void png_save_uint_32 (png_bytep buf, png_uint_32 i);
+
+void png_set_background (png_structp png_ptr, png_color_16p
+background_color, int background_gamma_code, int need_expand,
+double background_gamma);
+
+void png_set_bgr (png_structp png_ptr);
+
+void png_set_bKGD (png_structp png_ptr, png_infop info_ptr,
+png_color_16p background);
+
+void png_set_cHRM (png_structp png_ptr, png_infop info_ptr,
+double white_x, double white_y, double red_x, double red_y,
+double green_x, double green_y, double blue_x, double blue_y);
+
+void png_set_compression_level (png_structp png_ptr, int
+level);
+
+void png_set_compression_mem_level (png_structp png_ptr, int
+mem_level);
+
+void png_set_compression_method (png_structp png_ptr, int
+method);
+
+void png_set_compression_strategy (png_structp png_ptr, int
+strategy);
+
+void png_set_compression_window_bits (png_structp png_ptr, int
+window_bits);
+
+void png_set_crc_action (png_structp png_ptr, int crit_action,
+int ancil_action);
+
+void png_set_dither (png_structp png_ptr, png_colorp palette,
+int num_palette, int maximum_colors, png_uint_16p histogram,
+int full_dither);
+
+void png_set_error_fn (png_structp png_ptr, png_voidp
+error_ptr, png_error_ptr error_fn, png_error_ptr warning_fn);
+
+void png_set_expand (png_structp png_ptr);
+
+void png_set_filler (png_structp png_ptr, png_uint_32 filler,
+int flags);
+
+void png_set_filter (png_structp png_ptr, int method, int
+filters);
+
+void png_set_filter_heuristics (png_structp png_ptr, int
+heuristic_method, int num_weights, png_doublep filter_weights,
+png_doublep filter_costs);
+
+void png_set_flush (png_structp png_ptr, int nrows);
+
+void png_set_gamma (png_structp png_ptr, double screen_gamma,
+double default_file_gamma);
+
+void png_set_gAMA (png_structp png_ptr, png_infop info_ptr,
+double file_gamma);
+
+void png_set_gray_to_rgb (png_structp png_ptr);
+
+void png_set_hIST (png_structp png_ptr, png_infop info_ptr,
+png_uint_16p hist);
+
+int png_set_interlace_handling (png_structp png_ptr);
+
+void png_set_invert_alpha (png_structp png_ptr);
+
+void png_set_invert_mono (png_structp png_ptr);
+
+void png_set_IHDR (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 width, png_uint_32 height, int bit_depth, int
+color_type, int interlace_type, int compression_type, int
+filter_type);
+
+void png_set_oFFs (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 offset_x, png_uint_32 offset_y, int unit_type);
+
+void png_set_packing (png_structp png_ptr);
+
+void png_set_packswap (png_structp png_ptr);
+
+void png_set_pCAL (png_structp png_ptr, png_infop info_ptr,
+png_charp purpose, png_int_32 X0, png_int_32 X1, int type, int
+nparams, png_charp units, png_charpp params);
+
+void png_set_pHYs (png_structp png_ptr, png_infop info_ptr,
+png_uint_32 res_x, png_uint_32 res_y, int unit_type);
+
+void png_set_progressive_read_fn (png_structp png_ptr,
+png_voidp progressive_ptr, png_progressive_info_ptr info_fn,
+png_progressive_row_ptr row_fn, png_progressive_end_ptr
+end_fn);
+
+void png_set_PLTE (png_structp png_ptr, png_infop info_ptr,
+png_colorp palette, int num_palette);
+
+void png_set_read_fn (png_structp png_ptr, png_voidp io_ptr,
+png_rw_ptr read_data_fn);
+
+void png_set_rgb_to_gray (png_structp png_ptr);
+
+void png_set_sBIT (png_structp png_ptr, png_infop info_ptr,
+png_color_8p sig_bit);
+
+void png_set_shift (png_structp png_ptr, png_color_8p
+true_bits);
+
+void png_set_sig_bytes (png_structp png_ptr, int num_bytes);
+
+void png_set_sRGB (png_structp png_ptr, png_infop info_ptr, int
+intent);
+
+void png_set_sRGB_gAMA_and_cHRM (png_structp png_ptr, png_infop
+info_ptr, int intent);
+
+void png_set_strip_16 (png_structp png_ptr);
+
+void png_set_strip_alpha (png_structp png_ptr);
+
+void png_set_swap (png_structp png_ptr);
+
+void png_set_swap_alpha (png_structp png_ptr);
+
+void png_set_text (png_structp png_ptr, png_infop info_ptr,
+png_textp text_ptr, int num_text);
+
+void png_set_tIME (png_structp png_ptr, png_infop info_ptr,
+png_timep mod_time);
+
+void png_set_tRNS (png_structp png_ptr, png_infop info_ptr,
+png_bytep trans, int num_trans, png_color_16p trans_values);
+
+void png_set_write_fn (png_structp png_ptr, png_voidp io_ptr,
+png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn);
+
+int png_sig_cmp (png_bytep sig, png_size_t start, png_size_t
+num_to_check);
+
+void png_start_read_image (png_structp png_ptr);
+
+void png_warning (png_structp png_ptr, png_const_charp
+message);
+
+void png_write_bKGD (png_structp png_ptr, png_color_16p values,
+int color_type);
+
+void png_write_chunk (png_structp png_ptr, png_bytep
+chunk_name, png_bytep data, png_size_t length);
+
+void png_write_chunk_data (png_structp png_ptr, png_bytep data,
+png_size_t length);
+
+void png_write_chunk_end (png_structp png_ptr);
+
+void png_write_chunk_start (png_structp png_ptr, png_bytep
+chunk_name, png_uint_32 length);
+
+void png_write_cHRM (png_structp png_ptr, double white_x,
+double white_y, double red_x, double red_y, double green_x,
+double green_y, double blue_x, double blue_y);
+
+void png_write_data (png_structp png_ptr, png_bytep data,
+png_size_t length);
+
+void png_write_destroy (png_structp png_ptr);
+
+void png_write_destroy_info (png_infop info_ptr);
+
+void png_write_end (png_structp png_ptr, png_infop info_ptr);
+
+void png_write_filtered_row (png_structp png_ptr, png_bytep
+filtered_row);
+
+void png_write_find_filter (png_structp png_ptr, png_row_infop
+row_info);
+
+void png_write_finish_row (png_structp png_ptr);
+
+void png_write_flush (png_structp png_ptr);
+
+void png_write_gAMA (png_structp png_ptr, double file_gamma);
+
+void png_write_hIST (png_structp png_ptr, png_uint_16p hist,
+int num_hist);
+
+void png_write_image (png_structp png_ptr, png_bytepp image);
+
+void png_write_info (png_structp png_ptr, png_infop info_ptr);
+
+void png_write_init (png_structp png_ptr);
+
+void png_write_IDAT (png_structp png_ptr, png_bytep data,
+png_size_t length);
+
+void png_write_IEND (png_structp png_ptr);
+
+void png_write_IHDR (png_structp png_ptr, png_uint_32 width,
+png_uint_32 height, int bit_depth, int color_type, int
+compression_type, int filter_type, int interlace_type);
+
+void png_write_oFFs (png_structp png_ptr, png_uint_32 x_offset,
+png_uint_32 y_offset, int unit_type);
+
+void png_write_pCAL (png_structp png_ptr, png_charp purpose,
+png_int_32 X0, png_int_32 X1, int type, int nparams, png_charp
+units, png_charpp params);
+
+void png_write_pHYs (png_structp png_ptr, png_uint_32
+x_pixels_per_unit, png_uint_32 y_pixels_per_unit, int
+unit_type);
+
+void png_write_PLTE (png_structp png_ptr, png_colorp palette,
+png_uint_32 num_pal);
+
+void png_write_row (png_structp png_ptr, png_bytep row);
+
+void png_write_rows (png_structp png_ptr, png_bytepp row,
+png_uint_32 num_rows);
+
+void png_write_sBIT (png_structp png_ptr, png_color_8p sbit,
+int color_type);
+
+void png_write_sig (png_structp png_ptr);
+
+void png_write_sRGB (png_structp png_ptr, int intent);
+
+void png_write_start_row (png_structp png_ptr);
+
+void png_write_tEXt (png_structp png_ptr, png_charp key,
+png_charp text, png_size_t text_len);
+
+void png_write_tIME (png_structp png_ptr, png_timep mod_time);
+
+void png_write_tRNS (png_structp png_ptr, png_bytep trans,
+png_color_16p values, int number, int color_type);
+
+void png_write_zTXt (png_structp png_ptr, png_charp key,
+png_charp text, png_size_t text_len, int compression);
+
+voidpf png_zalloc (voidpf png_ptr, uInt items, uInt size);
+
+void png_zfree (voidpf png_ptr, voidpf ptr);
+
.SH DESCRIPTION
The
.I libpng
@@ -12,12 +702,1867 @@
the Portable Network Graphics (PNG) format image files. It uses the
.IR zlib(3)
compression library.
+Following is a copy of the libpng.txt file that accompanies libpng.
+.SH LIBPNG.TXT
+libpng.txt - A description on how to use and modify libpng
+
+ libpng version 0.99d
+ Updated and distributed by Glenn Randers-Pehrson
+ <randeg@alumni.rpi.edu>
+ Copyright (c) 1998, Glenn Randers-Pehrson
+ February 8, 1998
+
+ based on:
+
+ libpng 1.0 beta 6 version 0.96
+ Updated and distributed by Andreas Dilger
+ Copyright (c) 1996, 1997 Andreas Dilger
+ May 28, 1997
+
+ libpng 1.0 beta 2 - version 0.88
+ For conditions of distribution and use, see copyright
+ notice in png.h. Copyright (c) 1995, 1996 Guy Eric
+ Schalnat, Group 42, Inc. January 26, 1996
+
+ Updated/rewritten per request in the libpng FAQ
+ Copyright (c) 1995 Frank J. T. Wojcik
+ December 18, 1995 && January 20, 1996
+
+.SH I. Introduction
+
+This file describes how to use and modify the PNG reference library
+(known as libpng) for your own use. There are five sections to this
+file: introduction, structures, reading, writing, and modification and
+configuration notes for various special platforms. In addition to this
+file, example.c is a good starting point for using the library, as
+it is heavily commented and should include everything most people
+will need.
+
+Libpng was written as a companion to the PNG specification, as a way
+of reducing the amount of time and effort it takes to support the PNG
+file format in application programs. The PNG specification is available
+as RFC 2083 <ftp://ftp.uu.net/graphics/png/documents/> and as a
+W3C Recommendation <http://www.w3.org/TR/REC.png.html>. Some
+additional chunks are described in the special-purpose public chunks
+documents at <ftp://ftp.uu.net/graphics/png/documents/>. Other information
+about PNG can be found at the PNG home page, <http://www.cdrom.com/pub/png/>.
+
+Most users will not have to modify the library significantly; advanced
+users may want to modify it more. All attempts were made to make it as
+complete as possible, while keeping the code easy to understand.
+Currently, this library only supports C. Support for other languages
+is being considered.
+
+Libpng has been designed to handle multiple sessions at one time,
+to be easily modifiable, to be portable to the vast majority of
+machines (ANSI, K&R, 16-, 32-, and 64-bit) available, and to be easy
+to use. The ultimate goal of libpng is to promote the acceptance of
+the PNG file format in whatever way possible. While there is still
+work to be done (see the TODO file), libpng should cover the
+majority of the needs of its users.
+
+Libpng uses zlib for its compression and decompression of PNG files.
+The zlib compression utility is a general purpose utility that is
+useful for more than PNG files, and can be used without libpng.
+See the documentation delivered with zlib for more details.
+You can usually find the source files for the zlib utility wherever you
+find the libpng source files.
+
+Libpng is thread safe, provided the threads are using different
+instances of the structures. Each thread should have its own
+png_struct and png_info instances, and thus its own image.
+Libpng does not protect itself against two threads using the
+same instance of a structure.
+
+
+.SH II. Structures
+
+There are two main structures that are important to libpng, png_struct
+and png_info. The first, png_struct, is an internal structure that
+will not, for the most part, be used by a user except as the first
+variable passed to every libpng function call. It is not actually
+used in many of the functions; do not be alarmed about compiler
+warnings that say something to the effect that "png_ptr is not used."
+
+The png_info structure is designed to provide information about the
+PNG file. At one time, the fields of png_info were intended to be
+directly accessible to the user. However, this tended to cause problems
+with applications using dynamically loaded libraries, and as a result
+a set of interface functions for png_info was developed. The fields
+of png_info are still available for older applications, but it is
+suggested that applications use the new interfaces if at all possible.
+
+The png.h header file is an invaluable reference for programming with libpng.
+And while I'm on the topic, make sure you include the libpng header file:
+
+#include <png.h>
+
+.SH III. Reading
+
+Reading PNG files:
+
+We'll now walk you through the possible functions to call when reading
+in a PNG file, briefly explaining the syntax and purpose of each one.
+See example.c and png.h for more detail. While Progressive reading
+is covered in the next section, you will still need some of the
+functions discussed in this section to read a PNG file.
+
+You will want to do the I/O initialization(*) before you get into libpng,
+so if it doesn't work, you don't have much to undo. Of course, you
+will also want to insure that you are, in fact, dealing with a PNG
+file. Libpng provides a simple check to see if a file is a PNG file.
+To use it, pass in the first 1 to 8 bytes of the file, and it will
+return true or false (1 or 0) depending on whether the bytes could be
+part of a PNG file. Of course, the more bytes you pass in, the
+greater the accuracy of the prediction.
+
+If you are intending to keep the file pointer open for use in libpng,
+you must ensure you don't read more than 8 bytes from the beginning
+of the file, and you also have to make a call to png_set_sig_bytes_read()
+with the number of bytes you read from the beginning. Libpng will
+then only check the bytes (if any) that your program didn't read.
+
+(*): If you are not using the standard I/O functions, you will need
+to replace them with custom functions. See the discussion under
+Customizing libpng.
+
+
+ FILE *fp = fopen(file_name, "rb");
+ if (!fp)
+ {
+ return;
+ }
+ fread(header, 1, number, fp);
+ is_png = png_check_sig(header, 0, number);
+ if (!is_png)
+ {
+ return;
+ }
+
+
+Next, png_struct and png_info need to be allocated and initialized. In
+order to ensure that the size of these structures is correct even with a
+dynamically linked libpng, there are functions to initialize and
+allocate the structures. We also pass the library version, optional
+pointers to error handling functions, and a pointer to a data struct for
+use by the error functions, if necessary (the pointer and functions can
+be NULL if the default error handlers are to be used). See the section
+on Changes to Libpng below regarding the old initialization functions.
+
+ png_structp png_ptr = png_create_read_struct
+ (PNG_LIBPNG_VER_STRING, (void *)user_error_ptr,
+ user_error_fn, user_warning_fn);
+ if (!png_ptr)
+ return;
+
+ png_infop info_ptr = png_create_info_struct(png_ptr);
+ if (!info_ptr)
+ {
+ png_destroy_read_struct(&png_ptr,
+ (png_infopp)NULL, (png_infopp)NULL);
+ return;
+ }
+
+ png_infop end_info = png_create_info_struct(png_ptr);
+ if (!end_info)
+ {
+ png_destroy_read_struct(&png_ptr, &info_ptr,
+ (png_infopp)NULL);
+ return;
+ }
+
+
+The error handling routines passed to png_create_read_struct() are only
+necessary if you are not using the libpng supplied error handling
+functions. When libpng encounters an error, it expects to longjmp back
+to your routine. Therefore, you will need to call setjmp and pass the
+jmpbuf field of your png_struct. If you read the file from different
+routines, you will need to update the jmpbuf field every time you enter
+a new routine that will call a png_ function.
+
+See your documentation of setjmp/longjmp for your compiler for more
+handling in the Customizing Libpng section below for more information on
+the libpng error handling. If an error occurs, and libpng longjmp's
+back to your setjmp, you will want to call png_destroy_read_struct() to
+free any memory.
+
+ if (setjmp(png_ptr->jmpbuf))
+ {
+ png_destroy_read_struct(&png_ptr, &info_ptr,
+ &end_info);
+ fclose(fp);
+ return;
+ }
+
+Now you need to set up the input code. The default for libpng is to
+use the C function fread(). If you use this, you will need to pass a
+valid FILE * in the function png_init_io(). Be sure that the file is
+opened in binary mode. If you wish to handle reading data in another
+way, you need not call the png_init_io() function, but you must then
+implement the libpng I/O methods discussed in the Customizing Libpng
+section below.
+
+ png_init_io(png_ptr, fp);
+
+If you had previously opened the file and read any of the signature from
+the beginning in order to see if this was a PNG file, you need to let
+libpng know that there are some bytes missing from the start of the file.
+
+ png_set_sig_bytes(png_ptr, number);
+
+In PNG files, the alpha channel in an image is the level of opacity.
+If you need the alpha channel in an image to be the level of transparency
+instead of opacity, you can invert the alpha channel (or the tRNS chunk
+data) after it's read, so that 0 is fully opaque and 255 (in 8-bit or
+paletted images) or 65535 (in 16-bit images) is fully transparent, with
+
+ png_set_invert_alpha(png_ptr);
+
+This has to appear here rather than later with the other transformations
+because the tRNS chunk data must be modified in the case of paletted images.
+If your image is not a paletted image, the tRNS data (which in such cases
+represents a single color to be rendered as transparent) won't be changed.
+
+You are now ready to read all the file information up to the actual
+image data. You do this with a call to png_read_info().
+
+ png_read_info(png_ptr, info_ptr);
+
+Functions are used to get the information from the info_ptr:
+
+ png_get_IHDR(png_ptr, info_ptr, &width, &height,
+ &bit_depth, &color_type, &interlace_type,
+ &compression_type, &filter_type);
+
+ width - holds the width of the image
+ in pixels (up to 2^31).
+ height - holds the height of the image
+ in pixels (up to 2^31).
+ bit_depth - holds the bit depth of one of the
+ image channels. (valid values are
+ 1, 2, 4, 8, 16 and depend also on
+ the color_type. See also
+ significant bits (sBIT) below).
+ color_type - describes which color/alpha channels
+ are present.
+ PNG_COLOR_TYPE_GRAY
+ (bit depths 1, 2, 4, 8, 16)
+ PNG_COLOR_TYPE_GRAY_ALPHA
+ (bit depths 8, 16)
+ PNG_COLOR_TYPE_PALETTE
+ (bit depths 1, 2, 4, 8)
+ PNG_COLOR_TYPE_RGB
+ (bit_depths 8, 16)
+ PNG_COLOR_TYPE_RGB_ALPHA
+ (bit_depths 8, 16)
+
+ PNG_COLOR_MASK_PALETTE
+ PNG_COLOR_MASK_COLOR
+ PNG_COLOR_MASK_ALPHA
+
+ filter_type - (must be PNG_FILTER_TYPE_BASE
+ for PNG 1.0)
+ compression_type - (must be PNG_COMPRESSION_TYPE_BASE
+ for PNG 1.0)
+ interlace_type - (PNG_INTERLACE_TYPE_NONE or
+ PNG_INTERLACE_TYPE_ADAM7)
+ Any or all of interlace_type, compression_type, of
+ filter_type can be
+ NULL if you are not interested in their values.
+
+ channels = png_get_channels(png_ptr, info_ptr);
+ channels - number of channels of info for the
+ color type (valid values are 1 (GRAY,
+ PALETTE), 2 (GRAY_ALPHA), 3 (RGB),
+ 4 (RGB_ALPHA or RGB + filler byte))
+ rowbytes = png_get_rowbytes(png_ptr, info_ptr);
+ rowbytes - number of bytes needed to hold a row
+
+ signature = png_get_signature(png_ptr, info_ptr);
+ signature - holds the signature read from the
+ file (if any). The data is kept in
+ the same offset it would be if the
+ whole signature were read (ie if an
+ application had already read in 4
+ bytes of signature before starting
+ libpng, the remaining 4 bytes would
+ be in signature[4] through signature[7]
+ (see png_set_sig_bytes())).
+
+
+ width = png_get_image_width(png_ptr,
+ info_ptr);
+ height = png_get_image_height(png_ptr,
+ info_ptr);
+ bit_depth = png_get_bit_depth(png_ptr,
+ info_ptr);
+ color_type = png_get_color_type(png_ptr,
+ info_ptr);
+ filter_type = png_get_filter_type(png_ptr,
+ info_ptr);
+ compression_type = png_get_compression_type(png_ptr,
+ info_ptr);
+ interlace_type = png_get_interlace_type(png_ptr,
+ info_ptr);
+
+
+These are also important, but their validity depends on whether the chunk
+has been read. The png_get_valid(png_ptr, info_ptr, PNG_INFO_<chunk>) and
+png_get_<chunk>(png_ptr, info_ptr, ...) functions return non-zero if the
+data has been read, or zero if it is missing. The parameters to the
+png_get_<chunk> are set directly if they are simple data types, or a pointer
+into the info_ptr is returned for any complex types.
+
+ png_get_PLTE(png_ptr, info_ptr, &palette,
+ &num_palette);
+ palette - the palette for the file
+ (array of png_color)
+ num_palette - number of entries in the palette
+
+ png_get_gAMA(png_ptr, info_ptr, &gamma);
+ gamma - the gamma the file is written
+ at (PNG_INFO_gAMA)
+
+ png_get_sRGB(png_ptr, info_ptr, &srgb_intent);
+ srgb_intent - the rendering intent (PNG_INFO_sRGB)
+ The presence of the sRGB chunk
+ means that the pixel data is in the
+ sRGB color space. This chunk also
+ implies specific values of gAMA and
+ cHRM.
+
+ png_get_sBIT(png_ptr, info_ptr, &sig_bit);
+ sig_bit - the number of significant bits for
+ (PNG_INFO_sBIT) each of the gray,
+ red, green, and blue channels,
+ whichever are appropriate for the
+ given color type (png_color_16)
+
+ png_get_tRNS(png_ptr, info_ptr, &trans, &num_trans,
+ &trans_values);
+ trans - array of transparent entries for
+ palette (PNG_INFO_tRNS)
+ trans_values - transparent pixel for non-paletted
+ images (PNG_INFO_tRNS)
+ num_trans - number of transparent entries
+ (PNG_INFO_tRNS)
+
+ png_get_hIST(png_ptr, info_ptr, &hist);
+ (PNG_INFO_hIST)
+ hist - histogram of palette (array of
+ png_color_16)
+
+ png_get_tIME(png_ptr, info_ptr, &mod_time);
+ mod_time - time image was last modified
+ (PNG_VALID_tIME)
+
+ png_get_bKGD(png_ptr, info_ptr, &background);
+ background - background color (PNG_VALID_bKGD)
+
+ num_text = png_get_text(png_ptr, info_ptr, &text_ptr);
+ text_ptr - array of png_text holding image
+ comments
+ text_ptr[i]->key - keyword for comment.
+ text_ptr[i]->text - text comments for current
+ keyword.
+ text_ptr[i]->compression - type of compression used
+ on "text" PNG_TEXT_COMPRESSION_NONE
+ or PNG_TEXT_COMPRESSION_zTXt
+ num_text - number of comments
+
+ png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y,
+ &unit_type);
+ offset_x - positive offset from the left edge
+ of the screen
+ offset_y - positive offset from the top edge
+ of the screen
+ unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
+
+ png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y,
+ &unit_type);
+ res_x - pixels/unit physical resolution in
+ x direction
+ res_y - pixels/unit physical resolution in
+ x direction
+ unit_type - PNG_RESOLUTION_UNKOWN,
+ PNG_RESOLUTION_METER
+
+The data from the pHYs chunk can be retrieved in several convenient
+forms:
+
+ res_x_and_y = png_get_pixels_per_meter(png_ptr,
+ info_ptr)
+ aspect_ratio = png_get_pixel_aspect_ratio(png_ptr,
+ info_ptr)
+
+ (Each of these returns 0 [signifying "unknown"] if
+ the data is not present or if res_x is 0;
+ res_x_and_y is 0 if res_x != res_y)
+
+For more information, see the png_info definition in png.h and the
+PNG specification for chunk contents. Be careful with trusting
+rowbytes, as some of the transformations could increase the space
+needed to hold a row (expand, filler, gray_to_rgb, etc.).
+See png_read_update_info(), below.
+
+A quick word about text_ptr and num_text. PNG stores comments in
+keyword/text pairs, one pair per chunk, with no limit on the number
+of text chunks, and a 2^31 byte limit on their size. While there are
+suggested keywords, there is no requirement to restrict the use to these
+strings. It is strongly suggested that keywords and text be sensible
+to humans (that's the point), so don't use abbreviations. Non-printing
+symbols are not allowed. See the PNG specification for more details.
+There is also no requirement to have text after the keyword.
+
+Keywords should be limited to 79 Latin-1 characters without leading or
+trailing spaces, but non-consecutive spaces are allowed within the
+keyword. It is possible to have the same keyword any number of times.
+The text_ptr is an array of png_text structures, each holding pointer
+to a keyword and a pointer to a text string. Only the text string may
+be null. The keyword/text pairs are put into the array in the order
+that they are received. However, some or all of the text chunks may be
+after the image, so, to make sure you have read all the text chunks,
+don't mess with these until after you read the stuff after the image.
+This will be mentioned again below in the discussion that goes with
+png_read_end().
+
+After you've read the header information, you can set up the library
+to handle any special transformations of the image data. The various
+ways to transform the data will be described in the order that they
+should occur. This is important, as some of these change the color
+type and/or bit depth of the data, and some others only work on
+certain color types and bit depths. Even though each transformation
+checks to see if it has data that it can do somthing with, you should
+make sure to only enable a transformation if it will be valid for the
+data. For example, don't swap red and blue on grayscale data.
+
+The colors used for the background and transparency values should be
+supplied in the same format/depth as the current image data. They
+are stored in the same format/depth as the image data in a bKGD or tRNS
+chunk, so this is what libpng expects for this data. The colors are
+transformed to keep in sync with the image data when an application
+calls the png_read_update_info() routine (see below).
+
+Data will be decoded into the supplied row buffers packed into bytes
+unless the library has been told to transform it into another format.
+For example, 4 bit/pixel paletted or grayscale data will be returned
+2 pixels/byte with the leftmost pixel in the high-order bits of the
+byte, unless png_set_packing() is called. 8-bit RGB data will be stored
+in RGBRGBRGB format unless png_set_filler() is called to insert filler
+bytes, either before or after each RGB triplet. 16-bit RGB data will
+be returned RRGGBBRRGGBB, with the most significant byte of the color
+value first, unless png_set_strip_16() is called to transform it to
+regular RGBRGB triplets.
+
+The following code transforms grayscale images of less than 8 to 8 bits,
+changes paletted images to RGB, and adds a full alpha channel if there is
+transparency information in a tRNS chunk. This is most useful on
+grayscale images with bit depths of 2 or 4 or if there is a multiple-image
+viewing application that wishes to treat all images in the same way.
+
+ if (color_type == PNG_COLOR_TYPE_PALETTE &&
+ bit_depth <= 8) png_set_expand(png_ptr);
+
+ if (color_type == PNG_COLOR_TYPE_GRAY &&
+ bit_depth < 8) png_set_expand(png_ptr);
+
+ if (png_get_valid(png_ptr, info_ptr,
+ PNG_INFO_tRNS)) png_set_expand(png_ptr);
+
+PNG can have files with 16 bits per channel. If you only can handle
+8 bits per channel, this will strip the pixels down to 8 bit.
+
+ if (bit_depth == 16)
+ png_set_strip_16(png_ptr);
+
+The png_set_background() function tells libpng to composite images
+with alpha or simple transparency against the supplied background
+color. If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid),
+you may use this color, or supply another color more suitable for
+the current display (e.g., the background color from a web page). You
+need to tell libpng whether the color is in the gamma space of the
+display (PNG_BACKGROUND_GAMMA_SCREEN for colors you supply), the file
+(PNG_BACKGROUND_GAMMA_FILE for colors from the bKGD chunk), or one
+that is neither of these gammas (PNG_BACKGROUND_GAMMA_UNIQUE - I don't
+know why anyone would use this, but it's here).
+
+If, for some reason, you don't need the alpha channel on an image,
+and you want to remove it rather than combining it with the background
+(but the image author certainly had in mind that you *would* combine
+it with the background, so that's what you should probably do):
+
+ if (color_type & PNG_COLOR_MASK_ALPHA)
+ png_set_strip_alpha(png_ptr);
+
+PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
+they can, resulting in, for example, 8 pixels per byte for 1 bit
+files. This code expands to 1 pixel per byte without changing the
+values of the pixels:
+
+ if (bit_depth < 8)
+ png_set_packing(png_ptr);
+
+PNG files have possible bit depths of 1, 2, 4, 8, and 16. All pixels
+stored in a PNG image have been "scaled" or "shifted" up to the next
+higher possible bit depth (eg from 5 bits/sample in the range [0,31] to
+8 bits/sample in the range [0, 255]). However, it is also possible to
+convert the PNG pixel data back to the original bit depth of the image.
+This call reduces the pixels back down to the original bit depth:
+
+ png_color_16p sig_bit;
+
+ if (png_get_sBIT(png_ptr, info_ptr, &sig_bit))
+ png_set_shift(png_ptr, sig_bit);
+
+PNG files store 3-color pixels in red, green, blue order. This code
+changes the storage of the pixels to blue, green, red:
+
+ if (color_type == PNG_COLOR_TYPE_RGB ||
+ color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+ png_set_bgr(png_ptr);
+
+PNG files store RGB pixels packed into 3 bytes. This code expands them
+into 4 bytes for windowing systems that need them in this format:
+
+ if (bit_depth == 8 && color_type ==
+ PNG_COLOR_TYPE_RGB) png_set_filler(png_ptr,
+ filler, PNG_FILLER_BEFORE);
+
+where "filler" is the number to fill with, and the location is
+either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether
+you want the filler before the RGB or after. This transformation
+does not affect images that already have full alpha channels.
+
+If you are reading an image with an alpha channel, and you need the
+data as ARGB instead of the normal PNG format RGBA:
+
+ if (color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+ png_set_swap_alpha(png_ptr);
+
+For some uses, you may want a grayscale image to be represented as
+RGB. This code will do that conversion:
+
+ if (color_type == PNG_COLOR_TYPE_GRAY ||
+ color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+ png_set_gray_to_rgb(png_ptr);
+
+If you have a grayscale and you are using png_set_expand() to change to
+a higher bit-depth you must indicate if the supplied background gray
+is supplied in the original file bit depth (need_expand = 1) or in the
+expanded bit depth (need_expand = 0). Similarly, if you are reading
+a paletted image, you must indicate if you have supplied the background
+as a palette index that needs to be expanded (need_expand = 1). You can
+also specify an RGB triplet that isn't in the palette when setting your
+background for a paletted image.
+
+ png_color_16 my_background;
+ png_color_16p image_background;
+
+ if (png_get_bKGD(png_ptr, info_ptr,
+ &image_background))
+ png_set_background(png_ptr, image_background),
+ PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
+ else
+ png_set_background(png_ptr, &my_background,
+ PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
+
+To properly display PNG images on any kind of system, the application needs
+to know what the display gamma is. Ideally, the user will know this, and
+the application will allow them to set it. One method of allowing the user
+to set the display gamma separately for each system is to check for the
+DISPLAY_GAMMA and VIEWING_GAMMA environment variables or for a SCREEN_GAMMA
+environment variable, which will hopefully be correctly set.
+
+Note that display_gamma is the gamma of your display, while screen_gamma is
+the overall gamma correction required to produce pleasing results,
+which depends on the lighting conditions in the surrounding environment.
+Screen_gamma is display_gamma/viewing_gamma, where viewing_gamma is
+the amount of additional gamma correction needed to compensate for
+a dim (viewing_gamma=1.125) or dark (viewing_gamma=1.25) environment.
+In a brightly lit room, no compensation other than the display_gamma
+is needed (viewing_gamma=1.0).
+
+ if (/* We have a user-defined screen
+ gamma value */)
+ {
+ screen_gamma = user_defined_screen_gamma;
+ }
+ /* One way that applications can share the same
+ screen gamma value */
+ else if ((gamma_str = getenv("SCREEN_GAMMA"))
+ != NULL)
+ {
+ screen_gamma = atof(gamma_str);
+ }
+ /* If we don't have another value */
+ else
+ {
+ screen_gamma = 2.5; /* A good guess for a
+ PC monitor in a bright office */
+ screen_gamma = 2.2; /* A good guess for a
+ PC monitor in a dim room */
+ screen_gamma = 2.0; /* A good guess for a
+ PC monitor in a dark room */
+ screen_gamma = 1.7 or 1.0; /* A good
+ guess for Mac systems */
+ }
+
+The png_set_gamma() function handles gamma transformations of the data.
+Pass both the file gamma and the current screen_gamma. If the file does
+not have a gamma value, you can pass one anyway if you have an idea what
+it is (usually 0.50 is a good guess for GIF images on PCs). Note
+that file gammas are inverted from screen gammas. See the discussions
+on gamma in the PNG specification for an excellent description of what
+gamma is, and why all applications should support it. It is strongly
+recommended that PNG viewers support gamma correction.
+
+ if (png_get_gAMA(png_ptr, info_ptr, &gamma))
+ png_set_gamma(png_ptr, screen_gamma, gamma);
+ else
+ png_set_gamma(png_ptr, screen_gamma, 0.50);
+
+If you need to reduce an RGB file to a paletted file, or if a paletted
+file has more entries then will fit on your screen, png_set_dither()
+will do that. Note that this is a simple match dither that merely
+finds the closest color available. This should work fairly well with
+optimized palettes, and fairly badly with linear color cubes. If you
+pass a palette that is larger then maximum_colors, the file will
+reduce the number of colors in the palette so it will fit into
+maximum_colors. If there is a histogram, it will use it to make
+more intelligent choices when reducing the palette. If there is no
+histogram, it may not do as good a job.
+
+ if (color_type & PNG_COLOR_MASK_COLOR)
+ {
+ if (png_get_valid(png_ptr, info_ptr,
+ PNG_INFO_PLTE))
+ {
+ png_color_16p histogram;
+
+ png_get_hIST(png_ptr, info_ptr,
+ &histogram);
+ png_set_dither(png_ptr, palette, num_palette,
+ max_screen_colors, histogram, 1);
+ }
+ else
+ {
+ png_color std_color_cube[MAX_SCREEN_COLORS] =
+ { ... colors ... };
+
+ png_set_dither(png_ptr, std_color_cube,
+ MAX_SCREEN_COLORS, MAX_SCREEN_COLORS,
+ NULL,0);
+ }
+ }
+
+PNG files describe monochrome as black being zero and white being one.
+The following code will reverse this (make black be one and white be
+zero):
+
+ if (bit_depth == 1 && color_type == PNG_COLOR_GRAY)
+ png_set_invert_mono(png_ptr);
+
+PNG files store 16 bit pixels in network byte order (big-endian,
+ie. most significant bits first). This code chages the storage to the
+other way (little-endian, ie. least significant bits first, eg. the
+way PCs store them):
+
+ if (bit_depth == 16)
+ png_set_swap(png_ptr);
+
+If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
+need to change the order the pixels are packed into bytes, you can use:
+
+ if (bit_depth < 8)
+ png_set_packswap(png_ptr);
+
+The last thing to handle is interlacing; this is covered in detail below,
+but you must call the function here if you want libpng to handle expansion
+of the interlaced image.
+
+ number_of_passes = png_set_interlace_handling(png_ptr);
+
+After setting the transformations, libpng can update your png_info
+structure to reflect any transformations you've requested with this
+call. This is most useful to update the info structure's rowbytes
+field so you can use it to allocate your image memory. This function
+will also update your palette with the correct screen_gamma and
+background if these have been given with the calls above.
+
+ png_read_update_info(png_ptr, info_ptr);
+
+After you call png_read_update_info(), you can allocate any
+memory you need to hold the image. The row data is simply
+raw byte data for all forms of images. As the actual allocation
+varies among applications, no example will be given. If you
+are allocating one large chunk, you will need to build an
+array of pointers to each row, as it will be needed for some
+of the functions below.
+
+After you've allocated memory, you can read the image data.
+The simplest way to do this is in one function call. If you are
+allocating enough memory to hold the whole image, you can just
+call png_read_image() and libpng will read in all the image data
+and put it in the memory area supplied. You will need to pass in
+an array of pointers to each row.
+
+This function automatically handles interlacing, so you don't need
+to call png_set_interlace_handling() or call this function multiple
+times, or any of that other stuff necessary with png_read_rows().
+
+ png_read_image(png_ptr, row_pointers);
+
+where row_pointers is:
+
+ png_bytep row_pointers[height];
+
+You can point to void or char or whatever you use for pixels.
+
+If you don't want to read in the whole image at once, you can
+use png_read_rows() instead. If there is no interlacing (check
+interlace_type == PNG_INTERLACE_TYPE_NONE), this is simple:
+
+ png_read_rows(png_ptr, row_pointers, NULL,
+ number_of_rows);
+
+where row_pointers is the same as in the png_read_image() call.
+
+If you are doing this just one row at a time, you can do this with
+row_pointers:
+
+ png_bytep row_pointers = row;
+ png_read_row(png_ptr, &row_pointers, NULL);
+
+If the file is interlaced (info_ptr->interlace_type != 0), things get
+somewhat harder. The only current (PNG Specification version 1.0)
+interlacing type for PNG is (interlace_type == PNG_INTERLACE_TYPE_ADAM7)
+is a somewhat complicated 2D interlace scheme, known as Adam7, that
+breaks down an image into seven smaller images of varying size, based
+on an 8x8 grid.
+
+libpng can fill out those images or it can give them to you "as is".
+If you want them filled out, there are two ways to do that. The one
+mentioned in the PNG specification is to expand each pixel to cover
+those pixels that have not been read yet (the "rectangle" method).
+This results in a blocky image for the first pass, which gradually
+smooths out as more pixels are read. The other method is the "sparkle"
+method, where pixels are drawn only in their final locations, with the
+rest of the image remaining whatever colors they were initialized to
+before the start of the read. The first method usually looks better,
+but tends to be slower, as there are more pixels to put in the rows.
+
+If you don't want libpng to handle the interlacing details, just call
+png_read_rows() seven times to read in all seven images. Each of the
+images is a valid image by itself, or they can all be combined on an
+8x8 grid to form a single image (although if you intend to combine them
+you would be far better off using the libpng interlace handling).
+
+The first pass will return an image 1/8 as wide as the entire image
+(every 8th column starting in column 0) and 1/8 as high as the original
+(every 8th row starting in row 0), the second will be 1/8 as wide
+(starting in column 4) and 1/8 as high (also starting in row 0). The
+third pass will be 1/4 as wide (every 4th pixel starting in column 0) and
+1/8 as high (every 8th row starting in row 4), and the fourth pass will
+be 1/4 as wide and 1/4 as high (every 4th column starting in column 2,
+and every 4th row starting in row 0). The fifth pass will return an
+image 1/2 as wide, and 1/4 as high (starting at column 0 and row 2),
+while the sixth pass will be 1/2 as wide and 1/2 as high as the original
+(starting in column 1 and row 0). The seventh and final pass will be as
+wide as the original, and 1/2 as high, containing all of the odd
+numbered scanlines. Phew!
+
+If you want libpng to expand the images, call this before calling
+png_start_read_image() or png_read_update_info():
+
+ if (interlace_type == PNG_INTERLACE_TYPE_ADAM7)
+ number_of_passes
+ = png_set_interlace_handling(png_ptr);
+
+This will return the number of passes needed. Currently, this
+is seven, but may change if another interlace type is added.
+This function can be called even if the file is not interlaced,
+where it will return one pass.
+
+If you are not going to display the image after each pass, but are
+going to wait until the entire image is read in, use the sparkle
+effect. This effect is faster and the end result of either method
+is exactly the same. If you are planning on displaying the image
+after each pass, the "rectangle" effect is generally considered the
+better looking one.
+
+If you only want the "sparkle" effect, just call png_read_rows() as
+normal, with the third parameter NULL. Make sure you make pass over
+the image number_of_passes times, and you don't change the data in the
+rows between calls. You can change the locations of the data, just
+not the data. Each pass only writes the pixels appropriate for that
+pass, and assumes the data from previous passes is still valid.
+
+ png_read_rows(png_ptr, row_pointers, NULL,
+ number_of_rows);
+
+If you only want the first effect (the rectangles), do the same as
+before except pass the row buffer in the third parameter, and leave
+the second parameter NULL.
+
+ png_read_rows(png_ptr, NULL, row_pointers,
+ number_of_rows);
+
+After you are finished reading the image, you can finish reading
+the file. If you are interested in comments or time, which may be
+stored either before or after the image data, you should pass the
+separate png_info struct if you want to keep the comments from
+before and after the image separate. If you are not interested, you
+can pass NULL.
+
+ png_read_end(png_ptr, end_info);
+
+When you are done, you can free all memory allocated by libpng like this:
+
+ png_destroy_read_struct(&png_ptr, &info_ptr,
+ &end_info);
+
+For a more compact example of reading a PNG image, see the file example.c.
+
+
+Reading PNG files progressively:
+
+The progressive reader is slightly different then the non-progressive
+reader. Instead of calling png_read_info(), png_read_rows(), and
+png_read_end(), you make one call to png_process_data(), which calls
+callbacks when it has the info, a row, or the end of the image. You
+set up these callbacks with png_set_progressive_read_fn(). You don't
+have to worry about the input/output functions of libpng, as you are
+giving the library the data directly in png_process_data(). I will
+assume that you have read the section on reading PNG files above,
+so I will only highlight the differences (although I will show
+all of the code).
+
+png_structp png_ptr;
+png_infop info_ptr;
+
+ /* An example code fragment of how you would
+ initialize the progressive reader in your
+ application. */
+ int
+ initialize_png_reader()
+ {
+ png_ptr = png_create_read_struct
+ (PNG_LIBPNG_VER_STRING, (void *)user_error_ptr,
+ user_error_fn, user_warning_fn);
+ if (!png_ptr)
+ return -1;
+ info_ptr = png_create_info_struct(png_ptr);
+ if (!info_ptr)
+ {
+ png_destroy_read_struct(&png_ptr, (png_infopp)NULL,
+ (png_infopp)NULL);
+ return -1;
+ }
+
+ if (setjmp(png_ptr->jmpbuf))
+ {
+ png_destroy_read_struct(&png_ptr, &info_ptr,
+ (png_infopp)NULL);
+ return -1;
+ }
+
+ /* This one's new. You can provide functions
+ to be called when the header info is valid,
+ when each row is completed, and when the image
+ is finished. If you aren't using all functions,
+ you can specify a NULL parameter. You can use
+ any struct as the user_ptr (cast to a void pointer
+ for the function call), and retrieve the pointer
+ from inside the callbacks using the function
+
+ png_get_progressive_ptr(png_ptr);
+
+ which will return a void pointer, which you have
+ to cast appropriately.
+ */
+ png_set_progressive_read_fn(png_ptr, (void *)user_ptr,
+ info_callback, row_callback, end_callback);
+
+ return 0;
+ }
+
+ /* A code fragment that you call as you receive blocks
+ of data */
+ int
+ process_data(png_bytep buffer, png_uint_32 length)
+ {
+ if (setjmp(png_ptr->jmpbuf))
+ {
+ png_destroy_read_struct(&png_ptr, &info_ptr,
+ (png_infopp)NULL);
+ return -1;
+ }
+
+ /* This one's new also. Simply give it a chunk
+ of data from the file stream (in order, of
+ course). On machines with segmented memory
+ models machines, don't give it any more than
+ 64K. The library seems to run fine with sizes
+ of 4K. Although you can give it much less if
+ necessary (I assume you can give it chunks of
+ 1 byte, I haven't tried less then 256 bytes
+ yet). When this function returns, you may
+ want to display any rows that were generated
+ in the row callback if you don't already do
+ so there.
+ */
+ png_process_data(png_ptr, info_ptr, buffer, length);
+ return 0;
+ }
+
+ /* This function is called (as set by
+ png_set_progressive_fn() above) when enough data
+ has been supplied so all of the header has been
+ read.
+ */
+ void
+ {
+ /* Do any setup here, including setting any of
+ the transformations mentioned in the Reading
+ PNG files section. For now, you _must_ call
+ either png_start_read_image() or
+ png_read_update_info() after all the
+ transformations are set (even if you don't set
+ any). You may start getting rows before
+ png_process_data() returns, so this is your
+ last chance to prepare for that.
+ */
+ }
+
+ /* This function is called when each row of image
+ data is complete */
+ void
+ row_callback(png_structp png_ptr, png_bytep new_row,
+ png_uint_32 row_num, int pass)
+ {
+ /* If the image is interlaced, and you turned
+ on the interlace handler, this function will
+ be called for every row in every pass. Some
+ of these rows will not be changed from the
+ previous pass. When the row is not changed,
+ the new_row variable will be NULL. The rows
+ and passes are called in order, so you don't
+ really need the row_num and pass, but I'm
+ supplying them because it may make your life
+ easier.
+
+ For the non-NULL rows of interlaced images,
+ you must call png_progressive_combine_row()
+ passing in the row and the old row. You can
+ call this function for NULL rows (it will just
+ return) and for non-interlaced images (it just
+ does the memcpy for you) if it will make the
+ code easier. Thus, you can just do this for
+ all cases:
+ */
+
+ png_progressive_combine_row(png_ptr, old_row,
+ new_row);
+
+ /* where old_row is what was displayed for
+ previous rows. Note that the first pass
+ (pass == 0, really) will completely cover
+ the old row, so the rows do not have to be
+ initialized. After the first pass (and only
+ for interlaced images), you will have to pass
+ the current row, and the function will combine
+ the old row and the new row.
+ */
+ }
+
+ void
+ end_callback(png_structp png_ptr, png_infop info)
+ {
+ /* This function is called after the whole image
+ has been read, including any chunks after the
+ image (up to and including the IEND). You
+ will usually have the same info chunk as you
+ had in the header, although some data may have
+ been added to the comments and time fields.
+
+ Most people won't do much here, perhaps setting
+ a flag that marks the image as finished.
+ */
+ }
+
+
+
+IV. Writing
+
+Much of this is very similar to reading. However, everything of
+importance is repeated here, so you won't have to constantly look
+back up in the reading section to understand writing.
+
+You will want to do the I/O initialization before you get into libpng,
+so if it doesn't work, you don't have anything to undo. If you are not
+using the standard I/O functions, you will need to replace them with
+custom writing functions. See the discussion under Customizing libpng.
+
+ FILE *fp = fopen(file_name, "wb");
+ if (!fp)
+ {
+ return;
+ }
+
+Next, png_struct and png_info need to be allocated and initialized.
+As these can be both relatively large, you may not want to store these
+on the stack, unless you have stack space to spare. Of course, you
+will want to check if they return NULL.
+
+ png_structp png_ptr = png_create_write_struct
+ (PNG_LIBPNG_VER_STRING, (void *)user_error_ptr,
+ user_error_fn, user_warning_fn);
+ if (!png_ptr)
+ return;
+
+ png_infop info_ptr = png_create_info_struct(png_ptr);
+ if (!info_ptr)
+ {
+ png_destroy_write_struct(&png_ptr,
+ (png_infopp)NULL);
+ return;
+ }
+
+After you have these structures, you will need to set up the
+error handling. When libpng encounters an error, it expects to
+longjmp() back to your routine. Therefore, you will need to call
+setjmp and pass the jmpbuf field of your png_struct. If you
+write the file from different routines, you will need to update
+the jmpbuf field every time you enter a new routine that will
+call a png_ function. See your documentation of setjmp/longjmp
+for your compiler for more information on setjmp/longjmp. See
+the discussion on libpng error handling in the Customizing Libpng
+section below for more information on the libpng error handling.
+
+ if (setjmp(png_ptr->jmpbuf))
+ {
+ png_destroy_write_struct(&png_ptr, &info_ptr);
+ fclose(fp);
+ return;
+ }
+
+Now you need to set up the output code. The default for libpng is to
+use the C function fwrite(). If you use this, you will need to pass a
+valid FILE * in the function png_init_io(). Be sure that the file is
+opened in binary mode. Again, if you wish to handle writing data in
+another way, see the discussion on libpng I/O handling in the Customizing
+Libpng section below.
+
+ png_init_io(png_ptr, fp);
+
+You now have the option of modifying how the compression library will
+run. The following functions are mainly for testing, but may be useful
+in some cases, like if you need to write PNG files extremely fast and
+are willing to give up some compression, or if you want to get the
+maximum possible compression at the expense of slower writing. If you
+have no special needs in this area, let the library do what it wants by
+not calling this function at all, as it has been tuned to deliver a good
+speed/compression ratio. The second parameter to png_set_filter() is
+the filter method, for which the only valid value is '0' (as of the
+06/96 PNG specification. The third parameter is a flag that indicates
+which filter type(s) are to be tested for each scanline. See the
+Compression Library for details on the specific filter types.
+
+
+ /* turn on or off filtering, and/or choose
+ specific filters */
+ png_set_filter(png_ptr, 0,
+ PNG_FILTER_NONE | PNG_FILTER_SUB |
+ PNG_FILTER_PAETH);
+
+The png_set_compression_???() functions interface to the zlib compression
+library, and should mostly be ignored unless you really know what you are
+doing. The only generally useful call is png_set_compression_level()
+which changes how much time zlib spends on trying to compress the image
+data. See the Compression Library for details on the compression levels.
+
+ /* set the zlib compression level */
+ png_set_compression_level(png_ptr,
+ Z_BEST_COMPRESSION);
+
+ /* set other zlib parameters */
+ png_set_compression_mem_level(png_ptr, 8);
+ png_set_compression_strategy(png_ptr,
+ Z_DEFAULT_STRATEGY);
+ png_set_compression_window_bits(png_ptr, 15);
+ png_set_compression_method(png_ptr, 8);
+
+You now need to fill in the png_info structure with all the data you
+wish to write before the actual image. Note that the only thing you
+are allowed to write after the image is the text chunks and the time
+chunk (as of PNG Specification 1.0, anyway). See png_write_end() and
+the latest PNG specification for more information on that. If you
+wish to write them before the image, fill them in now, and flag that
+data as being valid. If you want to wait until after the data, don't
+fill them until png_write_end(). For all the fields in png_info and
+their data types, see png.h. For explanations of what the fields
+contain, see the PNG specification.
+
+Some of the more important parts of the png_info are:
+
+ png_set_IHDR(png_ptr, info_ptr, width, height,
+ bit_depth, color_type, interlace_type,
+ compression_type, filter_type)
+ width - holds the width of the image
+ in pixels (up to 2^31).
+ height - holds the height of the image
+ in pixels (up to 2^31).
+ bit_depth - holds the bit depth of one of the
+ image channels.
+ (valid values are 1, 2, 4, 8, 16
+ and depend also on the
+ color_type. See also significant
+ bits (sBIT) below).
+ color_type - describes which color/alpha
+ channels are present.
+ PNG_COLOR_TYPE_GRAY
+ (bit depths 1, 2, 4, 8, 16)
+ PNG_COLOR_TYPE_GRAY_ALPHA
+ (bit depths 8, 16)
+ PNG_COLOR_TYPE_PALETTE
+ (bit depths 1, 2, 4, 8)
+ PNG_COLOR_TYPE_RGB
+ (bit_depths 8, 16)
+ PNG_COLOR_TYPE_RGB_ALPHA
+ (bit_depths 8, 16)
+
+ PNG_COLOR_MASK_PALETTE
+ PNG_COLOR_MASK_COLOR
+ PNG_COLOR_MASK_ALPHA
+
+ interlace_type - PNG_INTERLACE_TYPE_NONE or
+ PNG_INTERLACE_TYPE_ADAM7
+ compression_type - (must be
+ PNG_COMPRESSION_TYPE_DEFAULT)
+ filter_type - (must be PNG_FILTER_TYPE_DEFAULT)
+
+ png_set_PLTE(png_ptr, info_ptr, palette,
+ num_palette);
+ palette - the palette for the file
+ (array of png_color)
+ num_palette - number of entries in the palette
+
+ png_set_gAMA(png_ptr, info_ptr, gamma);
+ gamma - the gamma the image was created
+ at (PNG_INFO_gAMA)
+
+ png_set_sRGB(png_ptr, info_ptr, srgb_intent);
+ srgb_intent - the rendering intent
+ (PNG_INFO_sRGB) The presence of
+ the sRGB chunk means that the pixel
+ data is in the sRGB color space.
+ This chunk also implies specific
+ values of gAMA and cHRM. Rendering
+ intent is the CSS-1 property that
+ has been defined by the International
+ Color Consortium
+ (http://www.color.org).
+ It can be one of
+ PNG_SRGB_INTENT_SATURATION,
+ PNG_SRGB_INTENT_PERCEPTUAL,
+ PNG_SRGB_INTENT_ABSOLUTE, or
+ PNG_SRGB_INTENT_RELATIVE.
+
+
+ png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr,
+ srgb_intent);
+ srgb_intent - the rendering intent
+ (PNG_INFO_sRGB) The presence of the
+ sRGB chunk means that the pixel
+ data is in the sRGB color space.
+ This function also causes gAMA and
+ cHRM chunks with the specific values
+ that are consistent with sRGB to be
+ written.
+
+ png_set_sBIT(png_ptr, info_ptr, sig_bit);
+ sig_bit - the number of significant bits for
+ (PNG_INFO_sBIT) each of the gray, red,
+ green, and blue channels, whichever are
+ appropriate for the given color type
+ (png_color_16)
+
+ png_set_tRNS(png_ptr, info_ptr, trans, num_trans,
+ trans_values);
+ trans - array of transparent entries for
+ palette (PNG_INFO_tRNS)
+ trans_values - transparent pixel for non-paletted
+ images (PNG_INFO_tRNS)
+ num_trans - number of transparent entries
+ (PNG_INFO_tRNS)
+
+ png_set_hIST(png_ptr, info_ptr, hist);
+ (PNG_INFO_hIST)
+ hist - histogram of palette (array of
+ png_color_16)
+
+ png_set_tIME(png_ptr, info_ptr, mod_time);
+ mod_time - time image was last modified
+ (PNG_VALID_tIME)
+
+ png_set_bKGD(png_ptr, info_ptr, background);
+ background - background color (PNG_VALID_bKGD)
+
+ png_set_text(png_ptr, info_ptr, text_ptr, num_text);
+ text_ptr - array of png_text holding image
+ comments
+ text_ptr[i]->key - keyword for comment.
+ text_ptr[i]->text - text comments for current
+ keyword.
+ text_ptr[i]->compression - type of compression used
+ on "text" PNG_TEXT_COMPRESSION_NONE or
+ PNG_TEXT_COMPRESSION_zTXt
+ num_text - number of comments in text_ptr
+
+ png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y,
+ unit_type);
+ offset_x - positive offset from the left
+ edge of the screen
+ offset_y - positive offset from the top
+ edge of the screen
+ unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
+
+ png_set_pHYs(png_ptr, info_ptr, res_x, res_y,
+ unit_type);
+ res_x - pixels/unit physical resolution
+ in x direction
+ res_y - pixels/unit physical resolution
+ in y direction
+ unit_type - PNG_RESOLUTION_UNKOWN,
+ PNG_RESOLUTION_METER
+
+In PNG files, the alpha channel in an image is the level of opacity.
+If your data is supplied as a level of transparency, you can invert the
+alpha channel before you write it, so that 0 is fully transparent and 255
+(in 8-bit or paletted images) or 65535 (in 16-bit images) is fully opaque,
+with
+
+ png_set_invert_alpha(png_ptr);
+
+This must appear here instead of later with the other transformations
+because in the case of paletted images the tRNS chunk data has to
+be inverted before the tRNS chunk is written. If your image is not a
+paletted image, the tRNS data (which in such cases represents a single
+color to be rendered as transparent) won't be changed.
+
+A quick word about text and num_text. text is an array of png_text
+structures. num_text is the number of valid structures in the array.
+If you want, you can use max_text to hold the size of the array, but
+libpng ignores it for writing (it does use it for reading). Each
+png_text structure holds a keyword-text value, and a compression type.
+The compression types have the same valid numbers as the compression
+types of the image data. Currently, the only valid number is zero.
+However, you can store text either compressed or uncompressed, unlike
+images which always have to be compressed. So if you don't want the
+text compressed, set the compression type to PNG_TEXT_COMPRESSION_NONE.
+Until text gets around 1000 bytes, it is not worth compressing it.
+After the text has been written out to the file, the compression type
+is set to PNG_TEXT_COMPRESSION_NONE_WR or PNG_TEXT_COMPRESSION_zTXt_WR,
+so that it isn't written out again at the end (in case you are calling
+png_write_end() with the same struct.
+
+The keywords that are given in the PNG Specification are:
+
+ Title Short (one line) title or
+ caption for image
+ Author Name of image's creator
+ Description Description of image (possibly long)
+ Copyright Copyright notice
+ Creation Time Time of original image creation
+ (usually RFC 1123 format, see below)
+ Software Software used to create the image
+ Disclaimer Legal disclaimer
+ Warning Warning of nature of content
+ Source Device used to create the image
+ Comment Miscellaneous comment; conversion
+ from other image format
+
+The keyword-text pairs work like this. Keywords should be short
+simple descriptions of what the comment is about. Some typical
+keywords are found in the PNG specification, as is some recomendations
+on keywords. You can repeat keywords in a file. You can even write
+some text before the image and some after. For example, you may want
+to put a description of the image before the image, but leave the
+disclaimer until after, so viewers working over modem connections
+don't have to wait for the disclaimer to go over the modem before
+they start seeing the image. Finally, keywords should be full
+words, not abbreviations. Keywords and text are in the ISO 8859-1
+(Latin-1) character set (a superset of regular ASCII) and can not
+contain NUL characters, and should not contain control or other
+unprintable characters. To make the comments widely readable, stick
+with basic ASCII, and avoid machine specific character set extensions
+like the IBM-PC character set. The keyword must be present, but
+you can leave off the text string on non-compressed pairs.
+Compressed pairs must have a text string, as only the text string
+is compressed anyway, so the compression would be meaningless.
+
+PNG supports modification time via the png_time structure. Two
+conversion routines are proved, png_convert_from_time_t() for
+time_t and png_convert_from_struct_tm() for struct tm. The
+time_t routine uses gmtime(). You don't have to use either of
+these, but if you wish to fill in the png_time structure directly,
+you should provide the time in universal time (GMT) if possible
+instead of your local time. Note that the year number is the full
+year (ie 1996, rather than 96 - PNG is year 2000 compliant!), and
+that months start with 1.
+
+If you want to store the time of the original image creation, you should
+use a plain tEXt chunk with the "Creation Time" keyword. This is
+necessary because the "creation time" of a PNG image is somewhat vague,
+depending on whether you mean the PNG file, the time the image was
+created in a non-PNG format, a still photo from which the image was
+scanned, or possibly the subject matter itself. In order to facilitate
+machine-readable dates, it is recommended that the "Creation Time"
+tEXt chunk use RFC 1123 format dates (eg 22 May 1997 18:07:10 GMT"),
+although this isn't a requirement. Unlike the tIME chunk, the
+"Creation Time" tEXt chunk is not expected to be automatically changed
+by the software. To facilitate the use of RFC 1123 dates, a function
+png_convert_to_rfc1123(png_timep) is provided to convert from PNG
+time to an RFC 1123 format string.
+
+You are now ready to write all the file information up to the actual
+image data. You do this with a call to png_write_info().
+
+ png_write_info(png_ptr, info_ptr);
+
+After you've written the file information, you can set up the library
+to handle any special transformations of the image data. The various
+ways to transform the data will be described in the order that they
+should occur. This is important, as some of these change the color
+type and/or bit depth of the data, and some others only work on
+certain color types and bit depths. Even though each transformation
+checks to see if it has data that it can do somthing with, you should
+make sure to only enable a transformation if it will be valid for the
+data. For example, don't swap red and blue on grayscale data.
+
+PNG files store RGB pixels packed into 3 bytes. This code tells
+the library to expect input data with 4 bytes per pixel
+
+ png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
+
+where the 0 is the value that will be put in the 4th byte, and the
+location is either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending
+upon whether the filler byte is stored XRGB or RGBX.
+
+PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
+they can, resulting in, for example, 8 pixels per byte for 1 bit files.
+If the data is supplied at 1 pixel per byte, use this code, which will
+correctly pack the pixels into a single byte:
+
+ png_set_packing(png_ptr);
+
+PNG files reduce possible bit depths to 1, 2, 4, 8, and 16. If your
+data is of another bit depth, you can write an sBIT chunk into the
+file so that decoders can get the original data if desired.
+
+ /* Set the true bit depth of the image data */
+ if (color_type & PNG_COLOR_MASK_COLOR)
+ {
+ sig_bit.red = true_bit_depth;
+ sig_bit.green = true_bit_depth;
+ sig_bit.blue = true_bit_depth;
+ }
+ else
+ {
+ sig_bit.gray = true_bit_depth;
+ }
+ if (color_type & PNG_COLOR_MASK_ALPHA)
+ {
+ sig_bit.alpha = true_bit_depth;
+ }
+
+ png_set_sBIT(png_ptr, info_ptr, &sig_bit);
+
+If the data is stored in the row buffer in a bit depth other than
+one supported by PNG (ie 3 bit data in the range 0-7 for a 4-bit PNG),
+this will scale the values to appear to be the correct bit depth as
+is required by PNG.
+
+ png_set_shift(png_ptr, &sig_bit);
+
+PNG files store 16 bit pixels in network byte order (big-endian,
+ie. most significant bits first). This code would be used if they are
+supplied the other way (little-endian, ie. least significant bits
+first, eg. the way PCs store them):
+
+ if (bit_depth > 8)
+ png_set_swap(png_ptr);
+
+If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
+need to change the order the pixels are packed into bytes, you can use:
+
+ if (bit_depth < 8)
+ png_set_packswap(png_ptr);
+
+PNG files store 3 color pixels in red, green, blue order. This code
+would be used if they are supplied as blue, green, red:
+
+ png_set_bgr(png_ptr);
+
+PNG files describe monochrome as black being zero and white being
+one. This code would be used if the pixels are supplied with this reversed
+(black being one and white being zero):
+
+ png_set_invert_mono(png_ptr);
+
+It is possible to have libpng flush any pending output, either manually,
+or automatically after a certain number of lines have been written. To
+flush the output stream a single time call:
+
+ png_write_flush(png_ptr);
+
+and to have libpng flush the output stream periodically after a certain
+number of scanlines have been written, call:
+
+ png_set_flush(png_ptr, nrows);
+
+Note that the distance between rows is from the last time png_write_flush()
+was called, or the first row of the image if it has never been called.
+So if you write 50 lines, and then png_set_flush 25, it will flush the
+output on the next scanline, and every 25 lines thereafter, unless
+png_write_flush()ls is called before 25 more lines have been written.
+If nrows is too small (less than about 10 lines for a 640 pixel wide
+RGB image) the image compression may decrease noticably (although this
+may be acceptable for real-time applications). Infrequent flushing will
+only degrade the compression performance by a few percent over images
+that do not use flushing.
+
+That's it for the transformations. Now you can write the image data.
+The simplest way to do this is in one function call. If have the
+whole image in memory, you can just call png_write_image() and libpng
+will write the image. You will need to pass in an array of pointers to
+each row. This function automatically handles interlacing, so you don't
+need to call png_set_interlace_handling() or call this function multiple
+times, or any of that other stuff necessary with png_write_rows().
+
+ png_write_image(png_ptr, row_pointers);
+
+where row_pointers is:
+
+ png_bytef *row_pointers[height];
+
+You can point to void or char or whatever you use for pixels.
+
+If you can't want to write the whole image at once, you can
+use png_write_rows() instead. If the file is not interlaced,
+this is simple:
+
+ png_write_rows(png_ptr, row_pointers,
+ number_of_rows);
+
+row_pointers is the same as in the png_write_image() call.
+
+If you are just writing one row at a time, you can do this with
+row_pointers:
+
+ png_bytep row_pointer = row;
+
+ png_write_row(png_ptr, &row_pointer);
+
+When the file is interlaced, things can get a good deal more
+complicated. The only currently (as of 6/96 -- PNG Specification
+version 1.0) defined interlacing scheme for PNG files is a
+compilcated interlace scheme, known as Adam7, that breaks down an
+image into seven smaller images of varying size. libpng will build
+these images for you, or you can do them yourself. If you want to
+build them yourself, see the PNG specification for details of which
+pixels to write when.
+
+If you don't want libpng to handle the interlacing details, just
+use png_set_interlace_handling() and call png_write_rows() the
+correct number of times to write all seven sub-images.
+
+If you want libpng to build the sub-images, call this before you start
+writing any rows:
+
+ number_of_passes =
+ png_set_interlace_handling(png_ptr);
+
+This will return the number of passes needed. Currently, this
+is seven, but may change if another interlace type is added.
+
+Then write the complete image number_of_passes times.
+
+ png_write_rows(png_ptr, row_pointers,
+ number_of_rows);
+
+As some of these rows are not used, and thus return immediately,
+you may want to read about interlacing in the PNG specification,
+and only update the rows that are actually used.
+
+After you are finished writing the image, you should finish writing
+the file. If you are interested in writing comments or time, you should
+pass an appropriately filled png_info pointer. If you are not interested,
+you can pass NULL.
+
+ png_write_end(png_ptr, info_ptr);
+
+When you are done, you can free all memory used by libpng like this:
+
+ png_destroy_write_struct(&png_ptr, &info_ptr);
+
+You must free any data you allocated for info_ptr, such as comments,
+palette, or histogram, before the call to png_destroy_write_struct();
+
+For a more compact example of writing a PNG image, see the file example.c.
+
+
+V. Modifying/Customizing libpng:
+
+There are two issues here. The first is changing how libpng does
+standard things like memory allocation, input/output, and error handling.
+The second deals with more complicated things like adding new chunks,
+adding new transformations, and generally changing how libpng works.
+
+All of the memory allocation, input/output, and error handling in libpng
+goes through callbacks which are user setable. The default routines are
+in pngmem.c, pngrio.c, pngwio.c, and pngerror.c respectively. To change
+these functions, call the approprate png_set_???_fn() function.
+
+Memory allocation is done through the functions png_large_malloc(),
+png_malloc(), png_realloc(), png_large_free(), and png_free(). These
+currently just call the standard C functions. The large functions must
+handle exactly 64K, but they don't have to handle more than that. If
+your pointers can't access more then 64K at a time, you will want to set
+MAXSEG_64K in zlib.h. Since it is unlikely that the method of handling
+memory allocation on a platform will change between applications, these
+functions must be modified in the library at compile time.
+
+Input/Output in libpng is done through png_read() and png_write(),
+which currently just call fread() and fwrite(). The FILE * is stored in
+png_struct and is initialized via png_init_io(). If you wish to change
+the method of I/O, the library supplies callbacks that you can set
+through the function png_set_read_fn() and png_set_write_fn() at run
+time, instead of calling the png_init_io() function. These functions
+also provide a void pointer that can be retrieved via the function
+png_get_io_ptr(). For example:
+
+ png_set_read_fn(png_structp png_ptr,
+ voidp io_ptr, png_rw_ptr read_data_fn)
+
+ png_set_write_fn(png_structp png_ptr,
+ voidp io_ptr, png_rw_ptr write_data_fn,
+ png_flush_ptr output_flush_fn);
+
+ voidp io_ptr = png_get_io_ptr(png_ptr);
+
+The replacement I/O functions should have prototypes as follows:
+
+ void user_read_data(png_structp png_ptr,
+ png_bytep data, png_uint_32 length);
+ void user_write_data(png_structp png_ptr,
+ png_bytep data, png_uint_32 length);
+ void user_flush_data(png_structp png_ptr);
+
+Supplying NULL for the read, write, or flush functions sets them back
+to using the default C stream functions. It is an error to read from
+a write stream, and vice versa.
+
+Error handling in libpng is done through png_error() and png_warning().
+Errors handled through png_error() are fatal, meaning that png_error()
+should never return to its caller. Currently, this is handled via
+setjmp() and longjmp(), but you could change this to do things like
+exit() if you should wish. On non-fatal errors, png_warning() is called
+to print a warning message, and then control returns to the calling code.
+By default png_error() and png_warning() print a message on stderr via
+fprintf() unless the library is compiled with PNG_NO_STDIO defined. If
+you wish to change the behavior of the error functions, you will need to
+set up your own message callbacks. These functions are normally supplied
+at the time that the png_struct is created. It is also possible to change
+these functions after png_create_???_struct() has been called by calling:
+
+ png_set_error_fn(png_structp png_ptr,
+ png_voidp error_ptr, png_error_ptr error_fn,
+ png_error_ptr warning_fn);
+
+ png_voidp error_ptr = png_get_error_ptr(png_ptr);
+
+If NULL is supplied for either error_fn or warning_fn, then the libpng
+default function will be used, calling fprintf() and/or longjmp() if a
+problem is encountered. The replacement error functions should have
+parameters as follows:
+
+ void user_error_fn(png_structp png_ptr,
+ png_const_charp error_msg);
+ void user_warning_fn(png_structp png_ptr,
+ png_const_charp warning_msg);
+
+The motivation behind using setjmp() and longjmp() is the C++ throw and
+catch exception handling methods. This makes the code much easier to write,
+as there is no need to check every return code of every function call.
+However, there are some uncertainties about the status of local variables
+after a longjmp, so the user may want to be careful about doing anything after
+setjmp returns non-zero besides returning itself. Consult your compiler
+documentation for more details.
+
+If you need to read or write custom chunks, you will need to get deeper
+into the libpng code, as a mechanism has not yet been supplied for user
+callbacks with custom chunks. First, read the PNG specification, and have
+a first level of understanding of how it works. Pay particular attention
+to the sections that describe chunk names, and look at how other chunks
+were designed, so you can do things similarly. Second, check out the
+sections of libpng that read and write chunks. Try to find a chunk that
+is similar to yours and copy off of it. More details can be found in the
+comments inside the code. A way of handling unknown chunks in a generic
+method, potentially via callback functions, would be best.
+
+If you wish to write your own transformation for the data, look through
+the part of the code that does the transformations, and check out some of
+the simpler ones to get an idea of how they work. Try to find a similar
+transformation to the one you want to add and copy off of it. More details
+can be found in the comments inside the code itself.
+
+Configuring for 16 bit platforms:
+
+You may need to change the png_large_malloc() and png_large_free()
+routines in pngmem.c, as these are requred to allocate 64K, although
+there is already support for many of the common DOS compilers. Also,
+you will want to look into zconf.h to tell zlib (and thus libpng) that
+it cannot allocate more then 64K at a time. Even if you can, the memory
+won't be accessable. So limit zlib and libpng to 64K by defining MAXSEG_64K.
+
+Configuring for DOS:
+
+For DOS users which only have access to the lower 640K, you will
+have to limit zlib's memory usage via a png_set_compression_mem_level()
+call. See zlib.h or zconf.h in the zlib library for more information.
+
+Configuring for Medium Model:
+
+Libpng's support for medium model has been tested on most of the popular
+compilers. Make sure MAXSEG_64K gets defined, USE_FAR_KEYWORD gets
+defined, and FAR gets defined to far in pngconf.h, and you should be
+all set. Everything in the library (except for zlib's structure) is
+expecting far data. You must use the typedefs with the p or pp on
+the end for pointers (or at least look at them and be careful). Make
+note that the row's of data are defined as png_bytepp which is a
+unsigned char far * far *.
+
+Configuring for gui/windowing platforms:
+
+You will need to write new error and warning functions that use the GUI
+interface, as described previously, and set them to be the error and
+warning functions at the time that png_create_???_struct() is called,
+in order to have them available during the structure initialization.
+They can be changed later via png_set_error_fn(). On some compliers,
+you may also have to change the memory allocators (png_malloc, etc.).
+
+Configuring for compiler xxx:
+
+All includes for libpng are in pngconf.h. If you need to add/change/delete
+an include, this is the place to do it. The includes that are not
+needed outside libpng are protected by the PNG_INTERNAL definition,
+which is only defined for those routines inside libpng itself. The
+files in libpng proper only include png.h, which includes pngconf.h.
+
+Configuring zlib:
+
+There are special functions to configure the compression. Perhaps the
+most useful one changes the compression level, which currently uses
+input compression values in the range 0 - 9. The library normally
+uses the default compression level (Z_DEFAULT_COMPRESSION = 6). Tests
+have shown that for a large majority of images, compression values in
+the range 3-6 compress nearly as well as higher levels, and do so much
+faster. For online applications it may be desirable to have maximum speed
+(Z_BEST_SPEED = 1). With versions of zlib after v0.99, you can also
+specify no compression (Z_NO_COMPRESSION = 0), but this would create
+files larger than just storing the raw bitmap. You can specify the
+compression level by calling:
+
+ png_set_compression_level(png_ptr, level);
+
+Another useful one is to reduce the memory level used by the library.
+The memory level defaults to 8, but it can be lowered if you are
+short on memory (running DOS, for example, where you only have 640K).
+
+ png_set_compression_mem_level(png_ptr, level);
+
+The other functions are for configuring zlib. They are not recommended
+for normal use and may result in writing an invalid PNG file. See
+zlib.h for more information on what these mean.
+
+ png_set_compression_strategy(png_ptr,
+ strategy);
+ png_set_compression_window_bits(png_ptr,
+ window_bits);
+ png_set_compression_method(png_ptr, method);
+
+Controlling row filtering:
+
+If you want to control whether libpng uses filtering or not, which
+filters are used, and how it goes about picking row filters, you
+can call one of these functions. The selection and configuration
+of row filters can have a significant impact on the size and
+encoding speed and a somewhat lesser impact on the decoding speed
+of an image. Filtering is enabled by default for RGB and grayscale
+images (with and without alpha), and for 8-bit paletted images, but
+not for paletted images with bit depths less than 8 bits/pixel.
+
+The 'method' parameter sets the main filtering method, which is
+currently only '0' in the PNG 1.0 specification. The 'filters'
+parameter sets which filter(s), if any, should be used for each
+scanline. Possible values are PNG_ALL_FILTERS and PNG_NO_FILTERS
+to turn filtering on and off, respectively.
+
+Individual filter types are PNG_FILTER_NONE, PNG_FILTER_SUB,
+PNG_FILTER_UP, PNG_FILTER_AVG, PNG_FILTER_PAETH, which can be bitwise
+ORed together '|' to specify one or more filters to use. These
+filters are described in more detail in the PNG specification. If
+you intend to change the filter type during the course of writing
+the image, you should start with flags set for all of the filters
+you intend to use so that libpng can initialize its internal
+structures appropriately for all of the filter types.
+
+ filters = PNG_FILTER_NONE | PNG_FILTER_SUB
+ | PNG_FILTER_UP;
+ png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE,
+ filters);
+
+It is also possible to influence how libpng chooses from among the
+available filters. This is done in two ways - by telling it how
+important it is to keep the same filter for successive rows, and
+by telling it the relative computational costs of the filters.
+
+ double weights[3] = {1.5, 1.3, 1.1},
+ costs[PNG_FILTER_VALUE_LAST] =
+ {1.0, 1.3, 1.3, 1.5, 1.7};
+
+ png_set_filter_selection(png_ptr,
+ PNG_FILTER_SELECTION_WEIGHTED, 3,
+ weights, costs);
+
+The weights are multiplying factors which indicate to libpng that row
+should be the same for successive rows unless another row filter is that
+many times better than the previous filter. In the above example, if
+the previous 3 filters were SUB, SUB, NONE, the SUB filter could have a
+"sum of absolute differences" 1.5 x 1.3 times higher than other filters
+and still be chosen, while the NONE filter could have a sum 1.1 times
+higher than other filters and still be chosen. Unspecified weights are
+taken to be 1.0, and the specified weights should probably be declining
+like those above in order to emphasize recent filters over older filters.
+
+The filter costs specify for each filter type a relative decoding cost
+to be considered when selecting row filters. This means that filters
+with higher costs are less likely to be chosen over filters with lower
+costs, unless their "sum of absolute differences" is that much smaller.
+The costs do not necessarily reflect the exact computational speeds of
+the various filters, since this would unduely influence the final image
+size.
+
+Note that the numbers above were invented purely for this example and
+are given only to help explain the function usage. Little testing has
+been done to find optimum values for either the costs or the weights.
+
+Removing unwanted object code:
+
+There are a bunch of #define's in pngconf.h that control what parts of
+libpng are compiled. All the defines end in _SUPPORTED. If you are
+never going to use an ability, you can change the #define to #undef
+before recompiling libpng and save yourself code and data space.
+You can also turn them off en masse with a compiler directive that
+defines PNG_READ[or WRITE]_NOT_FULLY_SUPPORTED, or
+PNG_READ[or WRITE]_ANCILLARY_CHUNKS_NOT_SUPPORTED, or all four,
+along with directives to turn on any of the capabilities that you do
+want. The NOT_FULLY_SUPPORTED directives disable the extra
+transformations but still leave the library fully capable of reading
+and writing PNG files with all known public chunks [except for sPLT].
+Use of the PNG_READ[or WRITE]_ANCILLARY_CHUNKS_NOT_SUPPORTED directive
+produces a library that is incapable of reading or writing ancillary chunks.
+
+All the reading and writing specific code are in separate files, so the
+linker should only grab the files it needs. However, if you want to
+make sure, or if you are building a stand alone library, all the
+reading files start with pngr and all the writing files start with
+pngw. The files that don't match either (like png.c, pngtrans.c, etc.)
+are used for both reading and writing, and always need to be included.
+The progressive reader is in pngpread.c
+
+If you are creating or distributing a dynamically linked library (a .so
+or DLL file), you should not remove or disable any parts of the library,
+as this will cause applications linked with different versions of the
+library to fail if they call functions not available in your library.
+The size of the library itself should not be an issue, because only
+those sections which are actually used will be loaded into memory.
+
+
+Changes to Libpng from version 0.88
+
+It should be noted that versions of libpng later than 0.96 are not
+distributed by the original libpng author, Guy Schalnat, nor by
+Andreas Dilger, who had taken over from Guy during 1996 and 1997, and
+distributed versions 0.89 through 0.96, but rather by another member
+of the original PNG Group, Glenn Randers-Pehrson. Guy and Andreas are
+still alive and well, but they have moved on to other things.
+
+The old libpng functions png_read_init(), png_write_init(),
+png_info_init(), png_read_destroy(), and png_write_destory() have been
+moved to PNG_INTERNAL in version 0.95 to discourage their use. The
+preferred method of creating and initializing the libpng structures is
+via the png_create_read_struct(), png_create_write_struct(), and
+png_create_info_struct() because they isolate the size of the structures
+from the application, allow version error checking, and also allow the
+use of custom error handling routines during the initialization, which
+the old functions do not. The functions png_read_destroy() and
+png_write_destroy() do not actually free the memory that libpng
+allocated for these structs, but just reset the data structures, so they
+can be used instead of png_destroy_read_struct() and
+png_destroy_write_struct() if you feel there is too much system overhead
+allocating and freeing the png_struct for each image read.
+
+Setting the error callbacks via png_set_message_fn() before
+png_read_init() as was suggested in libpng-0.88 is no longer supported
+because this caused applications which do not use custom error functions
+to fail if the png_ptr was not initialized to zero. It is still possible
+to set the error callbacks AFTER png_read_init(), or to change them with
+png_set_error_fn(), which is essentially the same function, but with a
+new name to force compilation errors with applications that try to use
+the old method.
+
+.SH NOTE
+
+Note about libpng version numbers:
+
+Due to various miscommunications, unforeseen code incompatibilities
+and occasional factors outside the authors' control, version numbering
+on the library has not always been consistent and straightforward.
+The following table summarizes matters since version 0.89c, which was
+the first widely used release:
+
+ source png.h shared-lib
+ version string version
+ ------- ------ ----------
+ 0.89c ("1.0 beta 3") 0.89 1.0.89
+ 0.90 ("1.0 beta 4") 0.90 0.90
+ [should have been 2.0.90]
+ 0.95 ("1.0 beta 5") 0.95 0.95
+ [should have been 2.0.95]
+ 0.96 ("1.0 beta 6") 0.96 0.96
+ [should have been 2.0.96]
+ 0.97b ("1.00.97 beta 7") 1.00.97 1.0.0
+ [should have been 2.0.97]
+ 0.97c 0.97 2.0.97
+ 0.98 0.98 2.0.98
+ 0.99 0.99 2.0.99
+ 0.99a 0.99 2.0.99
+ 0.99b 0.99 2.0.99
+ 0.99d 0.99 2.0.99
+ 1.0 1.00 2.1.0
+
+Henceforth the source version will match the shared-library minor
+and patch numbers; the shared-library major version number will be
+used for changes in backward compatibility, as it is intended.
+
.SH "SEE ALSO"
.IR libpng :
.IP
ftp://ftp.uu.net/graphics/png
http://www.cdrom.com/pub/png
-.LP
+
.IR zlib :
.IP
(generally) at the same location as
@@ -27,7 +2572,7 @@
ftp://ftp.uu.net/pub/archiving/zip/zlib
.br
http://www.cdrom.com/pub/infozip/zlib
-.LP
+
PNG specification:
RFC 2083
.IP
@@ -40,63 +2585,74 @@
or (as a W3C Recommendation) at
.br
http://www.w3.org/TR/REC-png.html
+
+In the case of any inconsistency between the PNG specification
+and this library, the specification takes precedence.
+
.SH AUTHORS
-This man page: R. P. C. Rodgers and Glenn Randers-Pehrson
-.LP
-Libpng version 0.99c (February 7, 1998):
+This man page: Glenn Randers-Pehrson
+<randeg@alumni.rpi.edu>
+
+Contributing Authors: John Bowler, Kevin Bracey, Sam Bushell, Andreas Dilger,
+Magnus Holmgren, Tom Lane, Dave Martindale, Glenn Randers-Pehrson,
+Greg Roelofs, Guy Eric Schalnat, Paul Schmidt, Tom Tanner, Tim Wegner.
+<png-implement@dworkin.wustl.edu>
+
+The contributing authors would like to thank all those who helped
+with testing, bug fixes, and patience. This wouldn't have been
+possible without all of you.
+
+Thanks to Frank J. T. Wojcik for helping with the documentation.
+
+Libpng version 0.99d (February 8, 1998):
Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
Currently maintained by Glenn Randers-Pehrson (randeg@alumni.rpi.edu).
-.LP
+
Supported by the PNG development group
.br
(png-implement@dworkin.wustl.edu).
-.LP
-.SH COPYRIGHT NOTICE
-Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
-.br
-Copyright (c) 1996, 1997 Andreas Dilger
-.br
-Copyright (c) 1998 Glenn Randers-Pehrson
-.br
+.SH BETA NOTICE
+This is a beta version. It reads and writes valid files on the
+platforms I have, and has had a wide testing program. You may
+have to modify the includes in png.h to get it to work on your
+system, and you may have to supply the correct compiler flags in
+the makefile if you can't find a makefile suitable for your
+operating system/compiler combination. Please contact the authors
+via the mailing list png-implement@dworkin.wustl.edu if you have any
+problems, or if you want your compiler/platform to be supported in
+the next official libpng release.
-.LP
-The PNG Reference Library is supplied "AS IS". The Contributing Authors
-and Group 42, Inc. disclaim all warranties, expressed or implied,
+.SH COPYRIGHT NOTICE:
+
+The PNG Reference Library (libpng) is supplied "AS IS". The Contributing
+Authors and Group 42, Inc. disclaim all warranties, expressed or implied,
including, without limitation, the warranties of merchantability and of
fitness for any purpose. The Contributing Authors and Group 42, Inc.
assume no liability for direct, indirect, incidental, special, exemplary,
or consequential damages, which may result from the use of the PNG
Reference Library, even if advised of the possibility of such damage.
-.LP
+
Permission is hereby granted to use, copy, modify, and distribute this
source code, or portions hereof, for any purpose, without fee, subject
to the following restrictions:
-.br
-1. The origin of this source code must not be misrepresented.
-.br
+ 1. The origin of this source code must not be
+ misrepresented.
-2. Altered versions must be plainly marked as such and must not be
-misrepresented as being the original source.
-.br
+ 2. Altered versions must be plainly marked as such
+ and must not be misrepresented as being the
+ original source.
-3. This Copyright notice may not be removed or altered from any source or
-altered source distribution.
-.br
+ 3. This Copyright notice may not be removed or
+ altered from any source or altered source
+ distribution.
-.LP
The Contributing Authors and Group 42, Inc. specifically permit, without
fee, and encourage the use of this source code as a component to
supporting the PNG file format in commercial products. If you use this
source code in a product, acknowledgment is not required but would be
appreciated.
-.LP
-The
-.IR zlib (3)
-library, version 1.0.8,
-is copyright (C) 1995-1998 by Jean-loup Gailly and Mark Adler.
-.LP
.\" end of man page
diff --git a/libpng.txt b/libpng.txt
index 93bd4ea..cceec1d 100644
--- a/libpng.txt
+++ b/libpng.txt
@@ -1,25 +1,25 @@
-libpng.txt - a description on how to use and modify libpng
+libpng.txt - A description on how to use and modify libpng
- libpng version 0.99c
- Updated and distributed by Glenn Randers-Pehrson <randeg@alumni.rpi.edu>
- Copyright (c) 1998, Glenn Randers-Pehrson
- February 7, 1998
+libpng version 0.99d
+Updated and distributed by Glenn Randers-Pehrson <randeg@alumni.rpi.edu>
+Copyright (c) 1998, Glenn Randers-Pehrson
+February 8, 1998
- based on:
+based on:
- libpng 1.0 beta 6 version 0.96
- Updated and distributed by Andreas Dilger
- Copyright (c) 1996, 1997 Andreas Dilger
- May 28, 1997
+libpng 1.0 beta 6 version 0.96
+Updated and distributed by Andreas Dilger
+Copyright (c) 1996, 1997 Andreas Dilger
+May 28, 1997
- libpng 1.0 beta 2 - version 0.88
- For conditions of distribution and use, see copyright notice in png.h
- Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
- January 26, 1996
+libpng 1.0 beta 2 - version 0.88
+For conditions of distribution and use, see copyright notice in png.h
+Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
+January 26, 1996
- Updated/rewritten per request in the libpng FAQ
- Copyright (c) 1995 Frank J. T. Wojcik
- December 18, 1995 && January 20, 1996
+Updated/rewritten per request in the libpng FAQ
+Copyright (c) 1995 Frank J. T. Wojcik
+December 18, 1995 && January 20, 1996
I. Introduction
@@ -68,7 +68,6 @@
same instance of a structure.
-
II. Structures
There are two main structures that are important to libpng, png_struct
@@ -91,8 +90,6 @@
#include <png.h>
-
-
III. Reading
Reading PNG files:
@@ -122,6 +119,7 @@
to replace them with custom functions. See the discussion under
Customizing libpng.
+
FILE *fp = fopen(file_name, "rb");
if (!fp)
{
@@ -134,6 +132,7 @@
return;
}
+
Next, png_struct and png_info need to be allocated and initialized. In
order to ensure that the size of these structures is correct even with a
dynamically linked libpng, there are functions to initialize and
@@ -143,25 +142,29 @@
be NULL if the default error handlers are to be used). See the section
on Changes to Libpng below regarding the old initialization functions.
- png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
- (void *)user_error_ptr, user_error_fn, user_warning_fn);
+ png_structp png_ptr = png_create_read_struct
+ (PNG_LIBPNG_VER_STRING, (void *)user_error_ptr,
+ user_error_fn, user_warning_fn);
if (!png_ptr)
return;
png_infop info_ptr = png_create_info_struct(png_ptr);
if (!info_ptr)
{
- png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
+ png_destroy_read_struct(&png_ptr,
+ (png_infopp)NULL, (png_infopp)NULL);
return;
}
png_infop end_info = png_create_info_struct(png_ptr);
if (!end_info)
{
- png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
+ png_destroy_read_struct(&png_ptr, &info_ptr,
+ (png_infopp)NULL);
return;
}
+
The error handling routines passed to png_create_read_struct() are only
necessary if you are not using the libpng supplied error handling
functions. When libpng encounters an error, it expects to longjmp back
@@ -171,7 +174,6 @@
a new routine that will call a png_ function.
See your documentation of setjmp/longjmp for your compiler for more
-information on setjmp/longjmp. See the discussion on libpng error
handling in the Customizing Libpng section below for more information on
the libpng error handling. If an error occurs, and libpng longjmp's
back to your setjmp, you will want to call png_destroy_read_struct() to
@@ -179,7 +181,8 @@
if (setjmp(png_ptr->jmpbuf))
{
- png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
+ png_destroy_read_struct(&png_ptr, &info_ptr,
+ &end_info);
fclose(fp);
return;
}
@@ -220,55 +223,80 @@
Functions are used to get the information from the info_ptr:
- png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,
- &interlace_type, &compression_type, &filter_type);
+ png_get_IHDR(png_ptr, info_ptr, &width, &height,
+ &bit_depth, &color_type, &interlace_type,
+ &compression_type, &filter_type);
- width - holds the width of the image in pixels (up to 2^31).
- height - holds the height of the image in pixels (up to 2^31).
- bit_depth - holds the bit depth of one of the image channels.
- (valid values are 1, 2, 4, 8, 16 and depend also on the
- color_type. See also significant bits (sBIT) below).
- color_type - describes which color/alpha channels are present.
- PNG_COLOR_TYPE_GRAY (bit depths 1, 2, 4, 8, 16)
- PNG_COLOR_TYPE_GRAY_ALPHA (bit depths 8, 16)
- PNG_COLOR_TYPE_PALETTE (bit depths 1, 2, 4, 8)
- PNG_COLOR_TYPE_RGB (bit_depths 8, 16)
- PNG_COLOR_TYPE_RGB_ALPHA (bit_depths 8, 16)
+ width - holds the width of the image
+ in pixels (up to 2^31).
+ height - holds the height of the image
+ in pixels (up to 2^31).
+ bit_depth - holds the bit depth of one of the
+ image channels. (valid values are
+ 1, 2, 4, 8, 16 and depend also on
+ the color_type. See also
+ significant bits (sBIT) below).
+ color_type - describes which color/alpha channels
+ are present.
+ PNG_COLOR_TYPE_GRAY
+ (bit depths 1, 2, 4, 8, 16)
+ PNG_COLOR_TYPE_GRAY_ALPHA
+ (bit depths 8, 16)
+ PNG_COLOR_TYPE_PALETTE
+ (bit depths 1, 2, 4, 8)
+ PNG_COLOR_TYPE_RGB
+ (bit_depths 8, 16)
+ PNG_COLOR_TYPE_RGB_ALPHA
+ (bit_depths 8, 16)
PNG_COLOR_MASK_PALETTE
PNG_COLOR_MASK_COLOR
PNG_COLOR_MASK_ALPHA
- filter_type - (must be PNG_FILTER_TYPE_BASE for PNG 1.0)
- compression_type - (must be PNG_COMPRESSION_TYPE_BASE for PNG 1.0)
- interlace_type - (PNG_INTERLACE_TYPE_NONE or PNG_INTERLACE_TYPE_ADAM7)
- Any or all of interlace_type, compression_type, of filter_type can be
+ filter_type - (must be PNG_FILTER_TYPE_BASE
+ for PNG 1.0)
+ compression_type - (must be PNG_COMPRESSION_TYPE_BASE
+ for PNG 1.0)
+ interlace_type - (PNG_INTERLACE_TYPE_NONE or
+ PNG_INTERLACE_TYPE_ADAM7)
+ Any or all of interlace_type, compression_type, of
+ filter_type can be
NULL if you are not interested in their values.
channels = png_get_channels(png_ptr, info_ptr);
- channels - number of channels of info for the color type
- (valid values are 1 (GRAY, PALETTE), 2 (GRAY_ALPHA),
- 3 (RGB), 4 (RGB_ALPHA or RGB + filler byte))
+ channels - number of channels of info for the
+ color type (valid values are 1 (GRAY,
+ PALETTE), 2 (GRAY_ALPHA), 3 (RGB),
+ 4 (RGB_ALPHA or RGB + filler byte))
rowbytes = png_get_rowbytes(png_ptr, info_ptr);
rowbytes - number of bytes needed to hold a row
signature = png_get_signature(png_ptr, info_ptr);
- signature - holds the signature read from the file (if any). The
- data is kept in the same offset it would be if the
- whole signature were read (ie if an application had
- already read in 4 bytes of signature before staring
- libpng, the remaining 4 bytes would be in signature[4]
- through signature[7] (see png_set_sig_bytes())).
-
-Information from each if the IHDR fields can be retrieve separately as well:
+ signature - holds the signature read from the
+ file (if any). The data is kept in
+ the same offset it would be if the
+ whole signature were read (ie if an
+ application had already read in 4
+ bytes of signature before starting
+ libpng, the remaining 4 bytes would
+ be in signature[4] through signature[7]
+ (see png_set_sig_bytes())).
- width = png_get_image_width(png_ptr, info_ptr);
- height = png_get_image_height(png_ptr, info_ptr);
- bit_depth = png_get_bit_depth(png_ptr, info_ptr);
- color_type = png_get_color_type(png_ptr, info_ptr);
- filter_type = png_get_filter_type(png_ptr, info_ptr);
- compression_type = png_get_compression_type(png_ptr, info_ptr);
- interlace_type = png_get_interlace_type(png_ptr, info_ptr);
+
+ width = png_get_image_width(png_ptr,
+ info_ptr);
+ height = png_get_image_height(png_ptr,
+ info_ptr);
+ bit_depth = png_get_bit_depth(png_ptr,
+ info_ptr);
+ color_type = png_get_color_type(png_ptr,
+ info_ptr);
+ filter_type = png_get_filter_type(png_ptr,
+ info_ptr);
+ compression_type = png_get_compression_type(png_ptr,
+ info_ptr);
+ interlace_type = png_get_interlace_type(png_ptr,
+ info_ptr);
These are also important, but their validity depends on whether the chunk
@@ -278,65 +306,91 @@
png_get_<chunk> are set directly if they are simple data types, or a pointer
into the info_ptr is returned for any complex types.
- png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette);
- palette - the palette for the file (array of png_color)
+ png_get_PLTE(png_ptr, info_ptr, &palette,
+ &num_palette);
+ palette - the palette for the file
+ (array of png_color)
num_palette - number of entries in the palette
png_get_gAMA(png_ptr, info_ptr, &gamma);
- gamma - the gamma the file is written at (PNG_INFO_gAMA)
+ gamma - the gamma the file is written
+ at (PNG_INFO_gAMA)
png_get_sRGB(png_ptr, info_ptr, &srgb_intent);
srgb_intent - the rendering intent (PNG_INFO_sRGB)
- The presence of the sRGB chunk means that the pixel
- data is in the sRGB color space. This chunk also
- implies specific values of gAMA and cHRM.
+ The presence of the sRGB chunk
+ means that the pixel data is in the
+ sRGB color space. This chunk also
+ implies specific values of gAMA and
+ cHRM.
png_get_sBIT(png_ptr, info_ptr, &sig_bit);
- sig_bit - the number of significant bits for (PNG_INFO_sBIT)
- the gray, red, green, and blue channels, whichever
- are appropriate for the given color type (png_color_16)
+ sig_bit - the number of significant bits for
+ (PNG_INFO_sBIT) each of the gray,
+ red, green, and blue channels,
+ whichever are appropriate for the
+ given color type (png_color_16)
- png_get_tRNS(png_ptr, info_ptr, &trans, &num_trans, &trans_values);
- trans - array of transparent entries for palette (PNG_INFO_tRNS)
- trans_values - transparent pixel for non-paletted images (PNG_INFO_tRNS)
- num_trans - number of transparent entries (PNG_INFO_tRNS)
+ png_get_tRNS(png_ptr, info_ptr, &trans, &num_trans,
+ &trans_values);
+ trans - array of transparent entries for
+ palette (PNG_INFO_tRNS)
+ trans_values - transparent pixel for non-paletted
+ images (PNG_INFO_tRNS)
+ num_trans - number of transparent entries
+ (PNG_INFO_tRNS)
- png_get_hIST(png_ptr, info_ptr, &hist); (PNG_INFO_hIST)
- hist - histogram of palette (array of png_color_16)
+ png_get_hIST(png_ptr, info_ptr, &hist);
+ (PNG_INFO_hIST)
+ hist - histogram of palette (array of
+ png_color_16)
png_get_tIME(png_ptr, info_ptr, &mod_time);
- mod_time - time image was last modified (PNG_VALID_tIME)
+ mod_time - time image was last modified
+ (PNG_VALID_tIME)
png_get_bKGD(png_ptr, info_ptr, &background);
background - background color (PNG_VALID_bKGD)
num_text = png_get_text(png_ptr, info_ptr, &text_ptr);
- text_ptr - array of png_text holding image comments
- text_ptr[i]->key - keyword for comment.
- text_ptr[i]->text - text comments for current keyword.
- text_ptr[i]->compression - type of compression used on "text"
- PNG_TEXT_COMPRESSION_NONE or
- PNG_TEXT_COMPRESSION_zTXt
+ text_ptr - array of png_text holding image
+ comments
+ text_ptr[i]->key - keyword for comment.
+ text_ptr[i]->text - text comments for current
+ keyword.
+ text_ptr[i]->compression - type of compression used
+ on "text" PNG_TEXT_COMPRESSION_NONE
+ or PNG_TEXT_COMPRESSION_zTXt
num_text - number of comments
- png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y, &unit_type);
- offset_x - positive offset from the left edge of the screen
- offset_y - positive offset from the top edge of the screen
+ png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y,
+ &unit_type);
+ offset_x - positive offset from the left edge
+ of the screen
+ offset_y - positive offset from the top edge
+ of the screen
unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
- png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y, &unit_type);
- res_x - pixels/unit physical resolution in x direction
- res_y - pixels/unit physical resolution in x direction
- unit_type - PNG_RESOLUTION_UNKOWN, PNG_RESOLUTION_METER
+ png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y,
+ &unit_type);
+ res_x - pixels/unit physical resolution in
+ x direction
+ res_y - pixels/unit physical resolution in
+ x direction
+ unit_type - PNG_RESOLUTION_UNKOWN,
+ PNG_RESOLUTION_METER
The data from the pHYs chunk can be retrieved in several convenient
forms:
- res_x_and_y = png_get_pixels_per_meter(png_ptr, info_ptr)
- aspect_ratio = png_get_pixel_aspect_ratio(png_ptr, info_ptr)
+ res_x_and_y = png_get_pixels_per_meter(png_ptr,
+ info_ptr)
+ aspect_ratio = png_get_pixel_aspect_ratio(png_ptr,
+ info_ptr)
- (Each of these returns 0 [signifying "unknown"] if the data is not
- present or if res_x is 0; res_x_and_y is 0 if res_x != res_y)
+ (Each of these returns 0 [signifying "unknown"] if
+ the data is not present or if res_x is 0;
+ res_x_and_y is 0 if res_x != res_y)
For more information, see the png_info definition in png.h and the
PNG specification for chunk contents. Be careful with trusting
@@ -399,14 +453,14 @@
grayscale images with bit depths of 2 or 4 or if there is a multiple-image
viewing application that wishes to treat all images in the same way.
- if (color_type == PNG_COLOR_TYPE_PALETTE && bit_depth <= 8)
- png_set_expand(png_ptr);
+ if (color_type == PNG_COLOR_TYPE_PALETTE &&
+ bit_depth <= 8) png_set_expand(png_ptr);
- if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
- png_set_expand(png_ptr);
+ if (color_type == PNG_COLOR_TYPE_GRAY &&
+ bit_depth < 8) png_set_expand(png_ptr);
- if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
- png_set_expand(png_ptr);
+ if (png_get_valid(png_ptr, info_ptr,
+ PNG_INFO_tRNS)) png_set_expand(png_ptr);
PNG can have files with 16 bits per channel. If you only can handle
8 bits per channel, this will strip the pixels down to 8 bit.
@@ -463,8 +517,9 @@
PNG files store RGB pixels packed into 3 bytes. This code expands them
into 4 bytes for windowing systems that need them in this format:
- if (bit_depth == 8 && color_type == PNG_COLOR_TYPE_RGB)
- png_set_filler(png_ptr, filler, PNG_FILLER_BEFORE);
+ if (bit_depth == 8 && color_type ==
+ PNG_COLOR_TYPE_RGB) png_set_filler(png_ptr,
+ filler, PNG_FILLER_BEFORE);
where "filler" is the number to fill with, and the location is
either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether
@@ -496,9 +551,10 @@
png_color_16 my_background;
png_color_16p image_background;
- if (png_get_bKGD(png_ptr, info_ptr, &image_background))
+ if (png_get_bKGD(png_ptr, info_ptr,
+ &image_background))
png_set_background(png_ptr, image_background),
- PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
+ PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
else
png_set_background(png_ptr, &my_background,
PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
@@ -519,22 +575,29 @@
In a brightly lit room, no compensation other than the display_gamma
is needed (viewing_gamma=1.0).
- if (/* We have a user-defined screen gamma value */)
+ if (/* We have a user-defined screen
+ gamma value */)
{
screen_gamma = user_defined_screen_gamma;
}
- /* One way that applications can share the same screen gamma value */
- else if ((gamma_str = getenv("SCREEN_GAMMA")) != NULL)
+ /* One way that applications can share the same
+ screen gamma value */
+ else if ((gamma_str = getenv("SCREEN_GAMMA"))
+ != NULL)
{
screen_gamma = atof(gamma_str);
}
/* If we don't have another value */
else
{
- screen_gamma = 2.5; /* A good guess for a PC monitor in a bright office */
- screen_gamma = 2.2; /* A good guess for a PC monitor in a dim room */
- screen_gamma = 2.0; /* A good guess for a PC monitor in a dark room */
- screen_gamma = 1.7 or 1.0; /* A good guess for Mac systems */
+ screen_gamma = 2.5; /* A good guess for a
+ PC monitor in a bright office */
+ screen_gamma = 2.2; /* A good guess for a
+ PC monitor in a dim room */
+ screen_gamma = 2.0; /* A good guess for a
+ PC monitor in a dark room */
+ screen_gamma = 1.7 or 1.0; /* A good
+ guess for Mac systems */
}
The png_set_gamma() function handles gamma transformations of the data.
@@ -564,21 +627,24 @@
if (color_type & PNG_COLOR_MASK_COLOR)
{
- if (png_get_valid(png_ptr, info_ptr, PNG_INFO_PLTE))
+ if (png_get_valid(png_ptr, info_ptr,
+ PNG_INFO_PLTE))
{
png_color_16p histogram;
- png_get_hIST(png_ptr, info_ptr, &histogram);
- png_set_dither(png_ptr, palette, num_palette, max_screen_colors,
- histogram, 1);
+ png_get_hIST(png_ptr, info_ptr,
+ &histogram);
+ png_set_dither(png_ptr, palette, num_palette,
+ max_screen_colors, histogram, 1);
}
else
{
png_color std_color_cube[MAX_SCREEN_COLORS] =
{ ... colors ... };
- png_set_dither(png_ptr, std_color_cube, MAX_SCREEN_COLORS,
- MAX_SCREEN_COLORS, NULL,0);
+ png_set_dither(png_ptr, std_color_cube,
+ MAX_SCREEN_COLORS, MAX_SCREEN_COLORS,
+ NULL,0);
}
}
@@ -649,7 +715,8 @@
use png_read_rows() instead. If there is no interlacing (check
interlace_type == PNG_INTERLACE_TYPE_NONE), this is simple:
- png_read_rows(png_ptr, row_pointers, NULL, number_of_rows);
+ png_read_rows(png_ptr, row_pointers, NULL,
+ number_of_rows);
where row_pointers is the same as in the png_read_image() call.
@@ -701,7 +768,8 @@
png_start_read_image() or png_read_update_info():
if (interlace_type == PNG_INTERLACE_TYPE_ADAM7)
- number_of_passes = png_set_interlace_handling(png_ptr);
+ number_of_passes
+ = png_set_interlace_handling(png_ptr);
This will return the number of passes needed. Currently, this
is seven, but may change if another interlace type is added.
@@ -722,18 +790,19 @@
not the data. Each pass only writes the pixels appropriate for that
pass, and assumes the data from previous passes is still valid.
- png_read_rows(png_ptr, row_pointers, NULL, number_of_rows);
+ png_read_rows(png_ptr, row_pointers, NULL,
+ number_of_rows);
If you only want the first effect (the rectangles), do the same as
before except pass the row buffer in the third parameter, and leave
the second parameter NULL.
- png_read_rows(png_ptr, NULL, row_pointers, number_of_rows);
+ png_read_rows(png_ptr, NULL, row_pointers,
+ number_of_rows);
After you are finished reading the image, you can finish reading
the file. If you are interested in comments or time, which may be
stored either before or after the image data, you should pass the
-info_ptr pointer from the png_read_info() call, or you can pass a
separate png_info struct if you want to keep the comments from
before and after the image separate. If you are not interested, you
can pass NULL.
@@ -742,7 +811,8 @@
When you are done, you can free all memory allocated by libpng like this:
- png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
+ png_destroy_read_struct(&png_ptr, &info_ptr,
+ &end_info);
For a more compact example of reading a PNG image, see the file example.c.
@@ -763,128 +833,155 @@
png_structp png_ptr;
png_infop info_ptr;
-/* An example code fragment of how you would initialize the progressive
- reader in your application. */
-int
-initialize_png_reader()
-{
- png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
- (void *)user_error_ptr, user_error_fn, user_warning_fn);
+ /* An example code fragment of how you would
+ initialize the progressive reader in your
+ application. */
+ int
+ initialize_png_reader()
+ {
+ png_ptr = png_create_read_struct
+ (PNG_LIBPNG_VER_STRING, (void *)user_error_ptr,
+ user_error_fn, user_warning_fn);
if (!png_ptr)
return -1;
info_ptr = png_create_info_struct(png_ptr);
if (!info_ptr)
{
- png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
+ png_destroy_read_struct(&png_ptr, (png_infopp)NULL,
+ (png_infopp)NULL);
return -1;
}
if (setjmp(png_ptr->jmpbuf))
{
- png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
+ png_destroy_read_struct(&png_ptr, &info_ptr,
+ (png_infopp)NULL);
return -1;
}
- /* This one's new. You can provide functions to be called
- when the header info is valid, when each row is completed,
- and when the image is finished. If you aren't using all
- functions, you can specify a NULL parameter. You can use
- any struct as the user_ptr (cast to a void pointer for the
- function call), and retrieve the pointer from inside the
- callbacks using the function png_get_progressive_ptr(png_ptr);
- which will return a void pointer, which you have to cast
- appropriately.
+ /* This one's new. You can provide functions
+ to be called when the header info is valid,
+ when each row is completed, and when the image
+ is finished. If you aren't using all functions,
+ you can specify a NULL parameter. You can use
+ any struct as the user_ptr (cast to a void pointer
+ for the function call), and retrieve the pointer
+ from inside the callbacks using the function
+
+ png_get_progressive_ptr(png_ptr);
+
+ which will return a void pointer, which you have
+ to cast appropriately.
*/
png_set_progressive_read_fn(png_ptr, (void *)user_ptr,
info_callback, row_callback, end_callback);
return 0;
-}
+ }
-/* A code fragment that you call as you recieve blocks of data */
-int
-process_data(png_bytep buffer, png_uint_32 length)
-{
+ /* A code fragment that you call as you receive blocks
+ of data */
+ int
+ process_data(png_bytep buffer, png_uint_32 length)
+ {
if (setjmp(png_ptr->jmpbuf))
{
- png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
+ png_destroy_read_struct(&png_ptr, &info_ptr,
+ (png_infopp)NULL);
return -1;
}
- /* This one's new also. Simply give it a chunk of data
- from the file stream (in order, of course). On machines
- with segmented memory models machines, don't give it any
- more than 64K. The library seems to run fine with sizes
- of 4K. Although you can give it much less if necessary
- (I assume you can give it chunks of 1 byte, I haven't
- tried less then 256 bytes yet). When this function returns,
- you may want to display any rows that were generated in the
- row callback if you don't already do so there.
+ /* This one's new also. Simply give it a chunk
+ of data from the file stream (in order, of
+ course). On machines with segmented memory
+ models machines, don't give it any more than
+ 64K. The library seems to run fine with sizes
+ of 4K. Although you can give it much less if
+ necessary (I assume you can give it chunks of
+ 1 byte, I haven't tried less then 256 bytes
+ yet). When this function returns, you may
+ want to display any rows that were generated
+ in the row callback if you don't already do
+ so there.
*/
png_process_data(png_ptr, info_ptr, buffer, length);
return 0;
-}
+ }
-/* This function is called (as set by png_set_progressive_fn() above)
- when enough data has been supplied so all of the header has been read.
+ /* This function is called (as set by
+ png_set_progressive_fn() above) when enough data
+ has been supplied so all of the header has been
+ read.
*/
-void
-info_callback(png_structp png_ptr, png_infop info)
-{
- /* Do any setup here, including setting any of the transformations
- mentioned in the Reading PNG files section. For now, you _must_
- call either png_start_read_image() or png_read_update_info()
- after all the transformations are set (even if you don't set
- any). You may start getting rows before png_process_data()
- returns, so this is your last chance to prepare for that.
+ void
+ {
+ /* Do any setup here, including setting any of
+ the transformations mentioned in the Reading
+ PNG files section. For now, you _must_ call
+ either png_start_read_image() or
+ png_read_update_info() after all the
+ transformations are set (even if you don't set
+ any). You may start getting rows before
+ png_process_data() returns, so this is your
+ last chance to prepare for that.
*/
-}
+ }
-/* This function is called when each row of image data is complete */
-void
-row_callback(png_structp png_ptr, png_bytep new_row,
+ /* This function is called when each row of image
+ data is complete */
+ void
+ row_callback(png_structp png_ptr, png_bytep new_row,
png_uint_32 row_num, int pass)
-{
- /* If the image is interlaced, and you turned on the interlace
- handler, this function will be called for every row in every pass.
- Some of these rows will not be changed from the previous pass.
- When the row is not changed, the new_row variable will be NULL.
- The rows and passes are called in order, so you don't really
- need the row_num and pass, but I'm supplying them because it
- may make your life easier.
+ {
+ /* If the image is interlaced, and you turned
+ on the interlace handler, this function will
+ be called for every row in every pass. Some
+ of these rows will not be changed from the
+ previous pass. When the row is not changed,
+ the new_row variable will be NULL. The rows
+ and passes are called in order, so you don't
+ really need the row_num and pass, but I'm
+ supplying them because it may make your life
+ easier.
- For the non-NULL rows of interlaced images, you must call
- png_progressive_combine_row() passing in the row and the
- old row. You can call this function for NULL rows (it will
- just return) and for non-interlaced images (it just does the
- memcpy for you) if it will make the code easier. Thus, you
- can just do this for all cases:
+ For the non-NULL rows of interlaced images,
+ you must call png_progressive_combine_row()
+ passing in the row and the old row. You can
+ call this function for NULL rows (it will just
+ return) and for non-interlaced images (it just
+ does the memcpy for you) if it will make the
+ code easier. Thus, you can just do this for
+ all cases:
*/
- png_progressive_combine_row(png_ptr, old_row, new_row);
+ png_progressive_combine_row(png_ptr, old_row,
+ new_row);
- /* where old_row is what was displayed for previous rows. Note
- that the first pass (pass == 0, really) will completely cover
- the old row, so the rows do not have to be initialized. After
- the first pass (and only for interlaced images), you will have
- to pass the current row, and the function will combine the
- old row and the new row.
+ /* where old_row is what was displayed for
+ previous rows. Note that the first pass
+ (pass == 0, really) will completely cover
+ the old row, so the rows do not have to be
+ initialized. After the first pass (and only
+ for interlaced images), you will have to pass
+ the current row, and the function will combine
+ the old row and the new row.
*/
-}
+ }
-void
-end_callback(png_structp png_ptr, png_infop info)
-{
- /* This function is called after the whole image has been read,
- including any chunks after the image (up to and including
- the IEND). You will usually have the same info chunk as you
- had in the header, although some data may have been added
- to the comments and time fields.
+ void
+ end_callback(png_structp png_ptr, png_infop info)
+ {
+ /* This function is called after the whole image
+ has been read, including any chunks after the
+ image (up to and including the IEND). You
+ will usually have the same info chunk as you
+ had in the header, although some data may have
+ been added to the comments and time fields.
- Most people won't do much here, perhaps setting a flag that
- marks the image as finished.
+ Most people won't do much here, perhaps setting
+ a flag that marks the image as finished.
*/
-}
+ }
@@ -910,15 +1007,17 @@
on the stack, unless you have stack space to spare. Of course, you
will want to check if they return NULL.
- png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING,
- (void *)user_error_ptr, user_error_fn, user_warning_fn);
+ png_structp png_ptr = png_create_write_struct
+ (PNG_LIBPNG_VER_STRING, (void *)user_error_ptr,
+ user_error_fn, user_warning_fn);
if (!png_ptr)
return;
png_infop info_ptr = png_create_info_struct(png_ptr);
if (!info_ptr)
{
- png_destroy_write_struct(&png_ptr, (png_infopp)NULL);
+ png_destroy_write_struct(&png_ptr,
+ (png_infopp)NULL);
return;
}
@@ -963,9 +1062,11 @@
Compression Library for details on the specific filter types.
- /* turn on or off filtering, and/or choose specific filters */
+ /* turn on or off filtering, and/or choose
+ specific filters */
png_set_filter(png_ptr, 0,
- PNG_FILTER_NONE | PNG_FILTER_SUB | PNG_FILTER_PAETH);
+ PNG_FILTER_NONE | PNG_FILTER_SUB |
+ PNG_FILTER_PAETH);
The png_set_compression_???() functions interface to the zlib compression
library, and should mostly be ignored unless you really know what you are
@@ -974,11 +1075,13 @@
data. See the Compression Library for details on the compression levels.
/* set the zlib compression level */
- png_set_compression_level(png_ptr, Z_BEST_COMPRESSION);
+ png_set_compression_level(png_ptr,
+ Z_BEST_COMPRESSION);
/* set other zlib parameters */
png_set_compression_mem_level(png_ptr, 8);
- png_set_compression_strategy(png_ptr, Z_DEFAULT_STRATEGY);
+ png_set_compression_strategy(png_ptr,
+ Z_DEFAULT_STRATEGY);
png_set_compression_window_bits(png_ptr, 15);
png_set_compression_method(png_ptr, 8);
@@ -995,91 +1098,136 @@
Some of the more important parts of the png_info are:
- png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, color_type,
- interlace_type, compression_type, filter_type)
- width - holds the width of the image in pixels (up to 2^31).
- height - holds the height of the image in pixels (up to 2^31).
- bit_depth - holds the bit depth of one of the image channels.
- (valid values are 1, 2, 4, 8, 16 and depend also on the
- color_type. See also significant bits (sBIT) below).
- color_type - describes which color/alpha channels are present.
- PNG_COLOR_TYPE_GRAY (bit depths 1, 2, 4, 8, 16)
- PNG_COLOR_TYPE_GRAY_ALPHA (bit depths 8, 16)
- PNG_COLOR_TYPE_PALETTE (bit depths 1, 2, 4, 8)
- PNG_COLOR_TYPE_RGB (bit_depths 8, 16)
- PNG_COLOR_TYPE_RGB_ALPHA (bit_depths 8, 16)
+ png_set_IHDR(png_ptr, info_ptr, width, height,
+ bit_depth, color_type, interlace_type,
+ compression_type, filter_type)
+ width - holds the width of the image
+ in pixels (up to 2^31).
+ height - holds the height of the image
+ in pixels (up to 2^31).
+ bit_depth - holds the bit depth of one of the
+ image channels.
+ (valid values are 1, 2, 4, 8, 16
+ and depend also on the
+ color_type. See also significant
+ bits (sBIT) below).
+ color_type - describes which color/alpha
+ channels are present.
+ PNG_COLOR_TYPE_GRAY
+ (bit depths 1, 2, 4, 8, 16)
+ PNG_COLOR_TYPE_GRAY_ALPHA
+ (bit depths 8, 16)
+ PNG_COLOR_TYPE_PALETTE
+ (bit depths 1, 2, 4, 8)
+ PNG_COLOR_TYPE_RGB
+ (bit_depths 8, 16)
+ PNG_COLOR_TYPE_RGB_ALPHA
+ (bit_depths 8, 16)
PNG_COLOR_MASK_PALETTE
PNG_COLOR_MASK_COLOR
PNG_COLOR_MASK_ALPHA
- interlace_type - PNG_INTERLACE_TYPE_NONE or PNG_INTERLACE_TYPE_ADAM7
- compression_type - (must be PNG_COMPRESSION_TYPE_DEFAULT for PNG 1.0)
- filter_type - (must be PNG_FILTER_TYPE_DEFAULT for PNG 1.0)
+ interlace_type - PNG_INTERLACE_TYPE_NONE or
+ PNG_INTERLACE_TYPE_ADAM7
+ compression_type - (must be
+ PNG_COMPRESSION_TYPE_DEFAULT)
+ filter_type - (must be PNG_FILTER_TYPE_DEFAULT)
- png_set_PLTE(png_ptr, info_ptr, palette, num_palette);
- palette - the palette for the file (array of png_color)
+ png_set_PLTE(png_ptr, info_ptr, palette,
+ num_palette);
+ palette - the palette for the file
+ (array of png_color)
num_palette - number of entries in the palette
png_set_gAMA(png_ptr, info_ptr, gamma);
- gamma - the gamma the image was created at (PNG_INFO_gAMA)
+ gamma - the gamma the image was created
+ at (PNG_INFO_gAMA)
png_set_sRGB(png_ptr, info_ptr, srgb_intent);
- srgb_intent - the rendering intent (PNG_INFO_sRGB)
- The presence of the sRGB chunk means that the pixel
- data is in the sRGB color space. This chunk also
- implies specific values of gAMA and cHRM.
- Rendering intent is the CSS-1 property that has been
- defined by the International Color Consortium
- (http://www.color.org). It can be one of
- PNG_SRGB_INTENT_SATURATION, PNG_SRGB_INTENT_PERCEPTUAL,
- PNG_SRGB_INTENT_ABSOLUTE, or PNG_SRGB_INTENT_RELATIVE.
+ srgb_intent - the rendering intent
+ (PNG_INFO_sRGB) The presence of
+ the sRGB chunk means that the pixel
+ data is in the sRGB color space.
+ This chunk also implies specific
+ values of gAMA and cHRM. Rendering
+ intent is the CSS-1 property that
+ has been defined by the International
+ Color Consortium
+ (http://www.color.org).
+ It can be one of
+ PNG_SRGB_INTENT_SATURATION,
+ PNG_SRGB_INTENT_PERCEPTUAL,
+ PNG_SRGB_INTENT_ABSOLUTE, or
+ PNG_SRGB_INTENT_RELATIVE.
- png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr, srgb_intent);
- srgb_intent - the rendering intent (PNG_INFO_sRGB)
- The presence of the sRGB chunk means that the pixel
- data is in the sRGB color space. This chunk also
- causes gAMA and cHRM chunks with the specific values
- that are consistent with sRGB to be written.
+ png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr,
+ srgb_intent);
+ srgb_intent - the rendering intent
+ (PNG_INFO_sRGB) The presence of the
+ sRGB chunk means that the pixel
+ data is in the sRGB color space.
+ This function also causes gAMA and
+ cHRM chunks with the specific values
+ that are consistent with sRGB to be
+ written.
png_set_sBIT(png_ptr, info_ptr, sig_bit);
- sig_bit - the number of significant bits for (PNG_INFO_sBIT)
- the gray, red, green, and blue channels, whichever
- are appropriate for the given color type (png_color_16)
+ sig_bit - the number of significant bits for
+ (PNG_INFO_sBIT) each of the gray, red,
+ green, and blue channels, whichever are
+ appropriate for the given color type
+ (png_color_16)
- png_set_tRNS(png_ptr, info_ptr, trans, num_trans, trans_values);
- trans - array of transparent entries for palette (PNG_INFO_tRNS)
- trans_values - transparent pixel for non-paletted images (PNG_INFO_tRNS)
- num_trans - number of transparent entries (PNG_INFO_tRNS)
+ png_set_tRNS(png_ptr, info_ptr, trans, num_trans,
+ trans_values);
+ trans - array of transparent entries for
+ palette (PNG_INFO_tRNS)
+ trans_values - transparent pixel for non-paletted
+ images (PNG_INFO_tRNS)
+ num_trans - number of transparent entries
+ (PNG_INFO_tRNS)
- png_set_hIST(png_ptr, info_ptr, hist); (PNG_INFO_hIST)
- hist - histogram of palette (array of png_color_16)
+ png_set_hIST(png_ptr, info_ptr, hist);
+ (PNG_INFO_hIST)
+ hist - histogram of palette (array of
+ png_color_16)
png_set_tIME(png_ptr, info_ptr, mod_time);
- mod_time - time image was last modified (PNG_VALID_tIME)
+ mod_time - time image was last modified
+ (PNG_VALID_tIME)
png_set_bKGD(png_ptr, info_ptr, background);
background - background color (PNG_VALID_bKGD)
png_set_text(png_ptr, info_ptr, text_ptr, num_text);
- text_ptr - array of png_text holding image comments
- text_ptr[i]->key - keyword for comment.
- text_ptr[i]->text - text comments for current keyword.
- text_ptr[i]->compression - type of compression used on "text"
- PNG_TEXT_COMPRESSION_NONE or
- PNG_TEXT_COMPRESSION_zTXt
- num_text - number of comments in text_ptr
+ text_ptr - array of png_text holding image
+ comments
+ text_ptr[i]->key - keyword for comment.
+ text_ptr[i]->text - text comments for current
+ keyword.
+ text_ptr[i]->compression - type of compression used
+ on "text" PNG_TEXT_COMPRESSION_NONE or
+ PNG_TEXT_COMPRESSION_zTXt
+ num_text - number of comments in text_ptr
- png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y, unit_type);
- offset_x - positive offset from the left edge of the screen
- offset_y - positive offset from the top edge of the screen
- unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
+ png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y,
+ unit_type);
+ offset_x - positive offset from the left
+ edge of the screen
+ offset_y - positive offset from the top
+ edge of the screen
+ unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
- png_set_pHYs(png_ptr, info_ptr, res_x, res_y, unit_type);
- res_x - pixels/unit physical resolution in x direction
- res_y - pixels/unit physical resolution in x direction
- unit_type - PNG_RESOLUTION_UNKOWN, PNG_RESOLUTION_METER
+ png_set_pHYs(png_ptr, info_ptr, res_x, res_y,
+ unit_type);
+ res_x - pixels/unit physical resolution
+ in x direction
+ res_y - pixels/unit physical resolution
+ in y direction
+ unit_type - PNG_RESOLUTION_UNKOWN,
+ PNG_RESOLUTION_METER
In PNG files, the alpha channel in an image is the level of opacity.
If your data is supplied as a level of transparency, you can invert the
@@ -1113,18 +1261,19 @@
The keywords that are given in the PNG Specification are:
- Title Short (one line) title or caption for image
- Author Name of image's creator
- Description Description of image (possibly long)
- Copyright Copyright notice
- Creation Time Time of original image creation (usually
- RFC 1123 format, see below)
- Software Software used to create the image
- Disclaimer Legal disclaimer
- Warning Warning of nature of content
- Source Device used to create the image
- Comment Miscellaneous comment; conversion from other
- image format
+ Title Short (one line) title or
+ caption for image
+ Author Name of image's creator
+ Description Description of image (possibly long)
+ Copyright Copyright notice
+ Creation Time Time of original image creation
+ (usually RFC 1123 format, see below)
+ Software Software used to create the image
+ Disclaimer Legal disclaimer
+ Warning Warning of nature of content
+ Source Device used to create the image
+ Comment Miscellaneous comment; conversion
+ from other image format
The keyword-text pairs work like this. Keywords should be short
simple descriptions of what the comment is about. Some typical
@@ -1296,7 +1445,8 @@
use png_write_rows() instead. If the file is not interlaced,
this is simple:
- png_write_rows(png_ptr, row_pointers, number_of_rows);
+ png_write_rows(png_ptr, row_pointers,
+ number_of_rows);
row_pointers is the same as in the png_write_image() call.
@@ -1323,14 +1473,16 @@
If you want libpng to build the sub-images, call this before you start
writing any rows:
- number_of_passes = png_set_interlace_handling(png_ptr);
+ number_of_passes =
+ png_set_interlace_handling(png_ptr);
This will return the number of passes needed. Currently, this
is seven, but may change if another interlace type is added.
Then write the complete image number_of_passes times.
- png_write_rows(png_ptr, row_pointers, number_of_rows);
+ png_write_rows(png_ptr, row_pointers,
+ number_of_rows);
As some of these rows are not used, and thus return immediately,
you may want to read about interlacing in the PNG specification,
@@ -1383,20 +1535,21 @@
also provide a void pointer that can be retrieved via the function
png_get_io_ptr(). For example:
- png_set_read_fn(png_structp png_ptr, voidp io_ptr,
- png_rw_ptr read_data_fn)
+ png_set_read_fn(png_structp png_ptr,
+ voidp io_ptr, png_rw_ptr read_data_fn)
- png_set_write_fn(png_structp png_ptr, voidp io_ptr,
- png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn);
+ png_set_write_fn(png_structp png_ptr,
+ voidp io_ptr, png_rw_ptr write_data_fn,
+ png_flush_ptr output_flush_fn);
voidp io_ptr = png_get_io_ptr(png_ptr);
The replacement I/O functions should have prototypes as follows:
- void user_read_data(png_structp png_ptr, png_bytep data,
- png_uint_32 length);
- void user_write_data(png_structp png_ptr, png_bytep data,
- png_uint_32 length);
+ void user_read_data(png_structp png_ptr,
+ png_bytep data, png_uint_32 length);
+ void user_write_data(png_structp png_ptr,
+ png_bytep data, png_uint_32 length);
void user_flush_data(png_structp png_ptr);
Supplying NULL for the read, write, or flush functions sets them back
@@ -1416,8 +1569,9 @@
at the time that the png_struct is created. It is also possible to change
these functions after png_create_???_struct() has been called by calling:
- png_set_error_fn(png_structp png_ptr, png_voidp error_ptr,
- png_error_ptr error_fn, png_error_ptr warning_fn);
+ png_set_error_fn(png_structp png_ptr,
+ png_voidp error_ptr, png_error_ptr error_fn,
+ png_error_ptr warning_fn);
png_voidp error_ptr = png_get_error_ptr(png_ptr);
@@ -1426,8 +1580,10 @@
problem is encountered. The replacement error functions should have
parameters as follows:
- void user_error_fn(png_structp png_ptr, png_const_charp error_msg);
- void user_warning_fn(png_structp png_ptr, png_const_charp warning_msg);
+ void user_error_fn(png_structp png_ptr,
+ png_const_charp error_msg);
+ void user_warning_fn(png_structp png_ptr,
+ png_const_charp warning_msg);
The motivation behind using setjmp() and longjmp() is the C++ throw and
catch exception handling methods. This makes the code much easier to write,
@@ -1523,8 +1679,10 @@
for normal use and may result in writing an invalid PNG file. See
zlib.h for more information on what these mean.
- png_set_compression_strategy(png_ptr, strategy);
- png_set_compression_window_bits(png_ptr, window_bits);
+ png_set_compression_strategy(png_ptr,
+ strategy);
+ png_set_compression_window_bits(png_ptr,
+ window_bits);
png_set_compression_method(png_ptr, method);
Controlling row filtering:
@@ -1553,8 +1711,10 @@
you intend to use so that libpng can initialize its internal
structures appropriately for all of the filter types.
- filters = PNG_FILTER_NONE | PNG_FILTER_SUB | PNG_FILTER_UP;
- png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, filters);
+ filters = PNG_FILTER_NONE | PNG_FILTER_SUB
+ | PNG_FILTER_UP;
+ png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE,
+ filters);
It is also possible to influence how libpng chooses from among the
available filters. This is done in two ways - by telling it how
@@ -1562,10 +1722,12 @@
by telling it the relative computational costs of the filters.
double weights[3] = {1.5, 1.3, 1.1},
- costs[PNG_FILTER_VALUE_LAST] = {1.0, 1.3, 1.3, 1.5, 1.7};
+ costs[PNG_FILTER_VALUE_LAST] =
+ {1.0, 1.3, 1.3, 1.5, 1.7};
- png_set_filter_selection(png_ptr, PNG_FILTER_SELECTION_WEIGHTED,
- 3, weights, costs);
+ png_set_filter_selection(png_ptr,
+ PNG_FILTER_SELECTION_WEIGHTED, 3,
+ weights, costs);
The weights are multiplying factors which indicate to libpng that row
should be the same for successive rows unless another row filter is that
@@ -1653,3 +1815,16 @@
png_set_error_fn(), which is essentially the same function, but with a
new name to force compilation errors with applications that try to use
the old method.
+.SH AUTHORS
+This man page: Glenn Randers-Pehrson
+
+Libpng version 0.99d (February 8, 1998):
+Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
+Currently maintained by Glenn Randers-Pehrson (randeg@alumni.rpi.edu).
+
+Supported by the PNG development group
+.br
+(png-implement@dworkin.wustl.edu).
+
+.\" end of man page
+
diff --git a/png.5 b/png.5
index c006411..ebe1d6f 100644
--- a/png.5
+++ b/png.5
@@ -1,4 +1,4 @@
-.TH PNG 5 "February 7, 1998"
+.TH PNG 5 "February 8, 1998"
.SH NAME
png \- Portable Network Graphics (PNG) format
.SH DESCRIPTION
diff --git a/png.c b/png.c
index 1601e80..93252fa 100644
--- a/png.c
+++ b/png.c
@@ -1,12 +1,12 @@
/* png.c - location for general purpose libpng functions
*
- * libpng 0.99c
+ * libpng 0.99d
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
- * February 7, 1998
+ * February 8, 1998
*/
#define PNG_INTERNAL
@@ -200,6 +200,7 @@
png_infop info_ptr;
png_debug(1, "in png_create_info_struct\n");
+ if(png_ptr == NULL) return (NULL);
if ((info_ptr = (png_infop)png_create_struct(PNG_STRUCT_INFO)) != NULL)
{
png_info_init(info_ptr);
diff --git a/png.h b/png.h
index 0e6362c..bd72712 100644
--- a/png.h
+++ b/png.h
@@ -1,12 +1,12 @@
/* png.h - header file for PNG reference library
*
- * libpng 0.99c beta
+ * libpng 0.99d beta
* For conditions of distribution and use, see the COPYRIGHT NOTICE below.
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998 Glenn Randers-Pehrson
- * February 7, 1998
+ * February 8, 1998
*
* Note about libpng version numbers:
*
@@ -30,6 +30,7 @@
* 0.99a 0.99 2.0.99
* 0.99b 0.99 2.0.99
* 0.99c 0.99 2.0.99
+ * 0.99d 0.99 2.0.99
* 1.0 1.00 2.1.0
*
* Henceforth the source version will match the shared-library minor
@@ -1109,10 +1110,10 @@
/* frees a pointer allocated by png_malloc() */
extern PNG_EXPORT(void,png_free) PNGARG((png_structp png_ptr, png_voidp ptr));
-extern PNG_EXPORT(void,png_buffered_memcpy) PNGARG((png_structp png_ptr,
+extern PNG_EXPORT(png_voidp,png_memcpy_check) PNGARG((png_structp png_ptr,
png_voidp s1, png_voidp s2, png_uint_32 size));
-extern PNG_EXPORT(void,png_buffered_memset) PNGARG((png_structp png_ptr,
+extern PNG_EXPORT(png_voidp,png_memset_check) PNGARG((png_structp png_ptr,
png_voidp s1, int value, png_uint_32 size));
#ifdef PNGTEST_MEMORY_DEBUG
@@ -1123,7 +1124,8 @@
png_voidp ptr));
#endif
#if defined(USE_FAR_KEYWORD) /* memory model conversion function */
-extern void *far_to_near PNGARG((png_structp png_ptr,png_voidp ptr,int check));
+extern void *png_far_to_near PNGARG((png_structp png_ptr,png_voidp ptr,
+ int check));
#endif /* USE_FAR_KEYWORD */
/* Fatal error in PNG image of libpng - can't continue */
@@ -1475,8 +1477,8 @@
#define PNG_FLAG_FREE_PALETTE 0x1000
#define PNG_FLAG_FREE_TRANS 0x2000
#define PNG_FLAG_FREE_HIST 0x4000
-#define PNG_FLAG_HAVE_CHUNK_HEADER 0x8000
-#define PNG_FLAG_WROTE_tIME 0x10000
+#define PNG_FLAG_HAVE_CHUNK_HEADER 0x8000L
+#define PNG_FLAG_WROTE_tIME 0x10000L
#define PNG_FLAG_CRC_ANCILLARY_MASK (PNG_FLAG_CRC_ANCILLARY_USE | \
PNG_FLAG_CRC_ANCILLARY_NOWARN)
diff --git a/pngconf.h b/pngconf.h
index 1829d61..1510b4f 100644
--- a/pngconf.h
+++ b/pngconf.h
@@ -1,12 +1,12 @@
/* pngconf.h - machine configurable file for libpng
*
- * libpng 0.99c
+ * libpng 0.99d
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
- * February 7, 1998
+ * February 8, 1998
*/
/* Any machine specific code is near the front of this file, so if you
@@ -525,8 +525,8 @@
/* use this to make far-to-near assignments */
# define CHECK 1
# define NOCHECK 0
-# define CVT_PTR(ptr) (far_to_near(png_ptr,ptr,CHECK))
-# define CVT_PTR_NOCHECK(ptr) (far_to_near(png_ptr,ptr,NOCHECK))
+# define CVT_PTR(ptr) (png_far_to_near(png_ptr,ptr,CHECK))
+# define CVT_PTR_NOCHECK(ptr) (png_far_to_near(png_ptr,ptr,NOCHECK))
# define png_strlen _fstrlen
# define png_memcmp _fmemcmp /* SJT: added */
# define png_memcpy _fmemcpy
diff --git a/pngerror.c b/pngerror.c
index 14e9a9e..30fb38f 100644
--- a/pngerror.c
+++ b/pngerror.c
@@ -1,12 +1,12 @@
/* pngerror.c - stub functions for i/o and memory allocation
*
- * libpng 0.99c
+ * libpng 0.99d
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
- * February 7, 1998
+ * February 8, 1998
*
* This file provides a location for all error handling. Users which
* need special error handling are expected to write replacement functions
diff --git a/pngget.c b/pngget.c
index 3e0eebf..fad5b03 100644
--- a/pngget.c
+++ b/pngget.c
@@ -1,12 +1,12 @@
/* pngget.c - retrieval of values from info struct
*
- * libpng 0.99c
+ * libpng 0.99d
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
- * February 7, 1998
+ * February 8, 1998
*/
#define PNG_INTERNAL
@@ -15,7 +15,7 @@
png_uint_32
png_get_valid(png_structp png_ptr, png_infop info_ptr, png_uint_32 flag)
{
- if (info_ptr != NULL)
+ if (png_ptr != NULL && info_ptr != NULL)
return(info_ptr->valid & flag);
else
return(0);
@@ -24,7 +24,7 @@
png_uint_32
png_get_rowbytes(png_structp png_ptr, png_infop info_ptr)
{
- if (info_ptr != NULL)
+ if (png_ptr != NULL && info_ptr != NULL)
return(info_ptr->rowbytes);
else
return(0);
@@ -35,7 +35,7 @@
png_uint_32
png_get_image_width(png_structp png_ptr, png_infop info_ptr)
{
- if (info_ptr != NULL)
+ if (png_ptr != NULL && info_ptr != NULL)
{
return info_ptr->width;
}
@@ -45,7 +45,7 @@
png_uint_32
png_get_image_height(png_structp png_ptr, png_infop info_ptr)
{
- if (info_ptr != NULL)
+ if (png_ptr != NULL && info_ptr != NULL)
{
return info_ptr->height;
}
@@ -55,7 +55,7 @@
png_byte
png_get_bit_depth(png_structp png_ptr, png_infop info_ptr)
{
- if (info_ptr != NULL)
+ if (png_ptr != NULL && info_ptr != NULL)
{
return info_ptr->bit_depth;
}
@@ -65,7 +65,7 @@
png_byte
png_get_color_type(png_structp png_ptr, png_infop info_ptr)
{
- if (info_ptr != NULL)
+ if (png_ptr != NULL && info_ptr != NULL)
{
return info_ptr->color_type;
}
@@ -75,7 +75,7 @@
png_byte
png_get_filter_type(png_structp png_ptr, png_infop info_ptr)
{
- if (info_ptr != NULL)
+ if (png_ptr != NULL && info_ptr != NULL)
{
return info_ptr->filter_type;
}
@@ -85,7 +85,7 @@
png_byte
png_get_interlace_type(png_structp png_ptr, png_infop info_ptr)
{
- if (info_ptr != NULL)
+ if (png_ptr != NULL && info_ptr != NULL)
{
return info_ptr->interlace_type;
}
@@ -95,7 +95,7 @@
png_byte
png_get_compression_type(png_structp png_ptr, png_infop info_ptr)
{
- if (info_ptr != NULL)
+ if (png_ptr != NULL && info_ptr != NULL)
{
return info_ptr->compression_type;
}
@@ -106,7 +106,7 @@
png_get_pixels_per_meter(png_structp png_ptr, png_infop info_ptr)
{
#if defined(PNG_READ_pHYs_SUPPORTED) || defined(PNG_WRITE_pHYs_SUPPORTED)
- if (info_ptr != NULL && info_ptr->valid & PNG_INFO_pHYs)
+ if (png_ptr != NULL && info_ptr != NULL && info_ptr->valid & PNG_INFO_pHYs)
{
png_debug1(1, "in %s retrieval function\n", "png_get_pixels_per_meter");
if(info_ptr->phys_unit_type != PNG_RESOLUTION_METER)
@@ -122,7 +122,7 @@
png_get_pixel_aspect_ratio(png_structp png_ptr, png_infop info_ptr)
{
#if defined(PNG_READ_pHYs_SUPPORTED) || defined(PNG_WRITE_pHYs_SUPPORTED)
- if (info_ptr != NULL && info_ptr->valid & PNG_INFO_pHYs)
+ if (png_ptr != NULL && info_ptr != NULL && info_ptr->valid & PNG_INFO_pHYs)
{
png_debug1(1, "in %s retrieval function\n", "png_get_aspect_ratio");
if (info_ptr->x_pixels_per_unit == 0)
@@ -140,7 +140,7 @@
png_get_x_offset_microns(png_structp png_ptr, png_infop info_ptr)
{
#if defined(PNG_READ_oFFs_SUPPORTED) || defined(PNG_WRITE_oFFs_SUPPORTED)
- if (info_ptr != NULL && info_ptr->valid & PNG_INFO_oFFs)
+ if (png_ptr != NULL && info_ptr != NULL && info_ptr->valid & PNG_INFO_oFFs)
{
png_debug1(1, "in %s retrieval function\n", "png_get_x_offset_microns");
if(info_ptr->offset_unit_type != PNG_OFFSET_MICROMETER)
@@ -156,7 +156,7 @@
png_get_y_offset_microns(png_structp png_ptr, png_infop info_ptr)
{
#if defined(PNG_READ_oFFs_SUPPORTED) || defined(PNG_WRITE_oFFs_SUPPORTED)
- if (info_ptr != NULL && info_ptr->valid & PNG_INFO_oFFs)
+ if (png_ptr != NULL && info_ptr != NULL && info_ptr->valid & PNG_INFO_oFFs)
{
png_debug1(1, "in %s retrieval function\n", "png_get_y_offset_microns");
if(info_ptr->offset_unit_type != PNG_OFFSET_MICROMETER)
@@ -172,7 +172,7 @@
png_get_x_offset_pixels(png_structp png_ptr, png_infop info_ptr)
{
#if defined(PNG_READ_oFFs_SUPPORTED) || defined(PNG_WRITE_oFFs_SUPPORTED)
- if (info_ptr != NULL && info_ptr->valid & PNG_INFO_oFFs)
+ if (png_ptr != NULL && info_ptr != NULL && info_ptr->valid & PNG_INFO_oFFs)
{
png_debug1(1, "in %s retrieval function\n", "png_get_x_offset_microns");
if(info_ptr->offset_unit_type != PNG_OFFSET_PIXEL)
@@ -188,7 +188,7 @@
png_get_y_offset_pixels(png_structp png_ptr, png_infop info_ptr)
{
#if defined(PNG_READ_oFFs_SUPPORTED) || defined(PNG_WRITE_oFFs_SUPPORTED)
- if (info_ptr != NULL && info_ptr->valid & PNG_INFO_oFFs)
+ if (png_ptr != NULL && info_ptr != NULL && info_ptr->valid & PNG_INFO_oFFs)
{
png_debug1(1, "in %s retrieval function\n", "png_get_y_offset_microns");
if(info_ptr->offset_unit_type != PNG_OFFSET_PIXEL)
@@ -206,7 +206,7 @@
png_byte
png_get_channels(png_structp png_ptr, png_infop info_ptr)
{
- if (info_ptr != NULL)
+ if (png_ptr != NULL && info_ptr != NULL)
return(info_ptr->channels);
else
return (0);
@@ -215,7 +215,7 @@
png_bytep
png_get_signature(png_structp png_ptr, png_infop info_ptr)
{
- if (info_ptr != NULL)
+ if (png_ptr != NULL && info_ptr != NULL)
return(info_ptr->signature);
else
return (NULL);
@@ -226,7 +226,7 @@
png_get_bKGD(png_structp png_ptr, png_infop info_ptr,
png_color_16p *background)
{
- if (info_ptr != NULL && info_ptr->valid & PNG_INFO_bKGD &&
+ if (png_ptr != NULL && info_ptr != NULL && info_ptr->valid & PNG_INFO_bKGD &&
background != NULL)
{
png_debug1(1, "in %s retrieval function\n", "bKGD");
@@ -243,7 +243,7 @@
double *white_x, double *white_y, double *red_x, double *red_y,
double *green_x, double *green_y, double *blue_x, double *blue_y)
{
- if (info_ptr != NULL && info_ptr->valid & PNG_INFO_cHRM)
+ if (png_ptr != NULL && info_ptr != NULL && info_ptr->valid & PNG_INFO_cHRM)
{
png_debug1(1, "in %s retrieval function\n", "cHRM");
if (white_x != NULL)
@@ -272,7 +272,7 @@
png_uint_32
png_get_gAMA(png_structp png_ptr, png_infop info_ptr, double *file_gamma)
{
- if (info_ptr != NULL && info_ptr->valid & PNG_INFO_gAMA &&
+ if (png_ptr != NULL && info_ptr != NULL && info_ptr->valid & PNG_INFO_gAMA &&
file_gamma != NULL)
{
png_debug1(1, "in %s retrieval function\n", "gAMA");
@@ -287,7 +287,7 @@
png_uint_32
png_get_sRGB(png_structp png_ptr, png_infop info_ptr, int *file_srgb_intent)
{
- if (info_ptr != NULL && info_ptr->valid & PNG_INFO_sRGB &&
+ if (png_ptr != NULL && info_ptr != NULL && info_ptr->valid & PNG_INFO_sRGB &&
file_srgb_intent != NULL)
{
png_debug1(1, "in %s retrieval function\n", "sRGB");
@@ -302,7 +302,8 @@
png_uint_32
png_get_hIST(png_structp png_ptr, png_infop info_ptr, png_uint_16p *hist)
{
- if (info_ptr != NULL && info_ptr->valid & PNG_INFO_hIST && hist != NULL)
+ if (png_ptr != NULL && info_ptr != NULL && info_ptr->valid & PNG_INFO_hIST &&
+ hist != NULL)
{
png_debug1(1, "in %s retrieval function\n", "hIST");
*hist = info_ptr->hist;
@@ -319,10 +320,9 @@
int *filter_type)
{
- if (info_ptr != NULL && width != NULL && height != NULL &&
+ if (png_ptr != NULL && info_ptr != NULL && width != NULL && height != NULL &&
bit_depth != NULL && color_type != NULL)
{
- png_uint_32 rowbytes;
int pixel_depth, channels;
png_uint_32 rowbytes_per_pixel;
@@ -349,7 +349,6 @@
channels++;
pixel_depth = *bit_depth * channels;
rowbytes_per_pixel = (pixel_depth + 7) >> 3;
- rowbytes = *width * rowbytes_per_pixel;
if ((*width > (png_uint_32)2147483647L/rowbytes_per_pixel))
{
png_warning(png_ptr,
@@ -365,7 +364,7 @@
png_get_oFFs(png_structp png_ptr, png_infop info_ptr,
png_uint_32 *offset_x, png_uint_32 *offset_y, int *unit_type)
{
- if (info_ptr != NULL && info_ptr->valid & PNG_INFO_oFFs &&
+ if (png_ptr != NULL && info_ptr != NULL && info_ptr->valid & PNG_INFO_oFFs &&
offset_x != NULL && offset_y != NULL && unit_type != NULL)
{
png_debug1(1, "in %s retrieval function\n", "oFFs");
@@ -384,7 +383,7 @@
png_charp *purpose, png_int_32 *X0, png_int_32 *X1, int *type, int *nparams,
png_charp *units, png_charpp *params)
{
- if (info_ptr != NULL && info_ptr->valid & PNG_INFO_pCAL &&
+ if (png_ptr != NULL && info_ptr != NULL && info_ptr->valid & PNG_INFO_pCAL &&
purpose != NULL && X0 != NULL && X1 != NULL && type != NULL &&
nparams != NULL && units != NULL && params != NULL)
{
@@ -409,7 +408,7 @@
{
png_uint_32 retval = 0;
- if (info_ptr != NULL && info_ptr->valid & PNG_INFO_pHYs)
+ if (png_ptr != NULL && info_ptr != NULL && info_ptr->valid & PNG_INFO_pHYs)
{
png_debug1(1, "in %s retrieval function\n", "pHYs");
if (res_x != NULL && res_y != NULL)
@@ -433,7 +432,8 @@
png_get_PLTE(png_structp png_ptr, png_infop info_ptr, png_colorp *palette,
int *num_palette)
{
- if (info_ptr != NULL && info_ptr->valid & PNG_INFO_PLTE && palette != NULL)
+ if (png_ptr != NULL && info_ptr != NULL && info_ptr->valid & PNG_INFO_PLTE &&
+ palette != NULL)
{
png_debug1(1, "in %s retrieval function\n", "PLTE");
*palette = info_ptr->palette;
@@ -448,7 +448,8 @@
png_uint_32
png_get_sBIT(png_structp png_ptr, png_infop info_ptr, png_color_8p *sig_bit)
{
- if (info_ptr != NULL && info_ptr->valid & PNG_INFO_sBIT && sig_bit != NULL)
+ if (png_ptr != NULL && info_ptr != NULL && info_ptr->valid & PNG_INFO_sBIT &&
+ sig_bit != NULL)
{
png_debug1(1, "in %s retrieval function\n", "sBIT");
*sig_bit = &(info_ptr->sig_bit);
@@ -463,7 +464,7 @@
png_get_text(png_structp png_ptr, png_infop info_ptr, png_textp *text_ptr,
int *num_text)
{
- if ((info_ptr != NULL) || (info_ptr->num_text > 0))
+ if (png_ptr != NULL && info_ptr != NULL || info_ptr->num_text > 0)
{
png_debug1(1, "in %s retrieval function\n",
(png_ptr->chunk_name[0] == '\0' ? "text"
@@ -482,7 +483,8 @@
png_uint_32
png_get_tIME(png_structp png_ptr, png_infop info_ptr, png_timep *mod_time)
{
- if (info_ptr != NULL && info_ptr->valid & PNG_INFO_tIME && mod_time != NULL)
+ if (png_ptr != NULL && info_ptr != NULL && info_ptr->valid & PNG_INFO_tIME &&
+ mod_time != NULL)
{
png_debug1(1, "in %s retrieval function\n", "tIME");
*mod_time = &(info_ptr->mod_time);
@@ -497,7 +499,7 @@
png_get_tRNS(png_structp png_ptr, png_infop info_ptr,
png_bytep *trans, int *num_trans, png_color_16p *trans_values)
{
- if (info_ptr != NULL && info_ptr->valid & PNG_INFO_tRNS)
+ if (png_ptr != NULL && info_ptr != NULL && info_ptr->valid & PNG_INFO_tRNS)
{
png_debug1(1, "in %s retrieval function\n", "tRNS");
if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE && trans != NULL)
diff --git a/pngmem.c b/pngmem.c
index 004288f..a698160 100644
--- a/pngmem.c
+++ b/pngmem.c
@@ -1,11 +1,11 @@
/* pngmem.c - stub functions for memory allocation
*
- * libpng 0.99c
+ * libpng 0.99d
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
- * February 7, 1998
+ * February 8, 1998
*
* This file provides a location for all memory allocation. Users which
* need special memory handling are expected to modify the code in this file
@@ -282,27 +282,22 @@
PNG_MALLOC(png_structp png_ptr, png_uint_32 size)
{
png_voidp ret;
- png_size_t length;
if (png_ptr == NULL || size == 0)
return ((png_voidp)NULL);
#ifdef PNG_MAX_MALLOC_64K
- if (png_size > (png_uint_32)65536L)
+ if (size > (png_uint_32)65536L)
png_error(png_ptr, "Cannot Allocate > 64K");
#endif
- length = (png_size_t)size;
- if ((png_uint_32)length != size)
- png_error(png_ptr, "Cannot Allocate > size_t");
-
#if defined(__TURBOC__) && !defined(__FLAT__)
- ret = farmalloc(length);
+ ret = farmalloc(size);
#else
# if defined(_MSC_VER) && defined(MAXSEG_64K)
- ret = halloc(length, 1);
+ ret = halloc(size, 1);
# else
- ret = malloc(length);
+ ret = malloc(size);
# endif
#endif
@@ -336,32 +331,29 @@
#endif /* Not Borland DOS special memory handler */
-void
-png_buffered_memcpy (png_structp png_ptr, png_voidp s1, png_voidp s2,
+png_voidp
+png_memcpy_check (png_structp png_ptr, png_voidp s1, png_voidp s2,
png_uint_32 length)
{
png_size_t size;
- png_uint_32 i;
- for (i=0; i<length; i+=65530)
- {
- size = (png_size_t)(length - i);
- if (size > (png_size_t)65530L)
- size=(png_size_t)65530L;
- png_memcpy (s1, s2, size);
- }
+
+ size = (png_size_t)length;
+ if ((png_uint_32)size != length)
+ png_error(png_ptr,"Overflow in png_memcpy_check.");
+
+ return(png_memcpy (s1, s2, size));
}
-void
-png_buffered_memset (png_structp png_ptr, png_voidp s1, int value,
+png_voidp
+png_memset_check (png_structp png_ptr, png_voidp s1, int value,
png_uint_32 length)
{
png_size_t size;
- png_uint_32 i;
- for (i=0; i<length; i+=65530)
- {
- size = length - i;
- if (size > 65530)
- size=65530;
- png_memset (s1, value, size);
- }
+
+ size = (png_size_t)length;
+ if ((png_uint_32)size != length)
+ png_error(png_ptr,"Overflow in png_memset_check.");
+
+ return (png_memset (s1, value, size));
+
}
diff --git a/pngpread.c b/pngpread.c
index 89d9226..23eb1de 100644
--- a/pngpread.c
+++ b/pngpread.c
@@ -1,12 +1,12 @@
/* pngpread.c - read a png file in push mode
*
- * libpng 0.99c
+ * libpng 0.99d
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
- * February 7, 1998
+ * February 8, 1998
*/
#define PNG_INTERNAL
@@ -638,7 +638,7 @@
png_ptr->row_buf + 1, png_ptr->prev_row + 1,
(int)(png_ptr->row_buf[0]));
- png_buffered_memcpy(png_ptr, png_ptr->prev_row, png_ptr->row_buf,
+ png_memcpy_check(png_ptr, png_ptr->prev_row, png_ptr->row_buf,
png_ptr->rowbytes + 1);
if (png_ptr->transformations)
@@ -774,8 +774,8 @@
if (png_ptr->interlaced)
{
png_ptr->row_number = 0;
- png_buffered_memset(png_ptr, png_ptr->prev_row, 0,
- (png_size_t)png_ptr->rowbytes + 1);
+ png_memset_check(png_ptr, png_ptr->prev_row, 0,
+ png_ptr->rowbytes + 1);
do
{
png_ptr->pass++;
@@ -806,7 +806,11 @@
png_push_handle_tEXt(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
{
if (png_ptr->mode == PNG_BEFORE_IHDR || png_ptr->mode & PNG_HAVE_IEND)
- png_error(png_ptr, "Out of place tEXt");
+ {
+ png_error(png_ptr, "Out of place tEXt");
+ /* to quiet some compiler warnings */
+ if(info_ptr == NULL) return;
+ }
#ifdef PNG_MAX_MALLOC_64K
png_ptr->skip_length = 0; /* This may not be necessary */
@@ -888,7 +892,11 @@
png_push_handle_zTXt(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
{
if (png_ptr->mode == PNG_BEFORE_IHDR || png_ptr->mode & PNG_HAVE_IEND)
- png_error(png_ptr, "Out of place zTXt");
+ {
+ png_error(png_ptr, "Out of place zTXt");
+ /* to quiet some compiler warnings */
+ if(info_ptr == NULL) return;
+ }
#ifdef PNG_MAX_MALLOC_64K
/* We can't handle zTXt chunks > 64K, since we don't have enough space
@@ -1073,6 +1081,8 @@
if (!(png_ptr->chunk_name[0] & 0x20))
{
png_chunk_error(png_ptr, "unknown critical chunk");
+ /* to quiet some compiler warnings */
+ if(info_ptr == NULL) return;
}
png_push_crc_skip(png_ptr, length);
diff --git a/pngread.c b/pngread.c
index d1d95c3..04ad665 100644
--- a/pngread.c
+++ b/pngread.c
@@ -1,12 +1,12 @@
/* pngread.c - read a PNG file
*
- * libpng 0.99c
+ * libpng 0.99d
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
- * February 7, 1998
+ * February 8, 1998
*
* This file contains routines that an application calls directly to
* read a PNG file or stream.
@@ -418,7 +418,7 @@
png_ptr->row_buf + 1, png_ptr->prev_row + 1,
(int)(png_ptr->row_buf[0]));
- png_buffered_memcpy(png_ptr, png_ptr->prev_row, png_ptr->row_buf,
+ png_memcpy_check(png_ptr, png_ptr->prev_row, png_ptr->row_buf,
png_ptr->rowbytes + 1);
if (png_ptr->transformations)
diff --git a/pngrio.c b/pngrio.c
index 3f950bf..43546ff 100644
--- a/pngrio.c
+++ b/pngrio.c
@@ -1,12 +1,12 @@
/* pngrio.c - functions for data input
*
- * libpng 0.99c
+ * libpng 0.99d
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
- * February 7, 1998
+ * February 8, 1998
*
* This file provides a location for all input. Users which need
* special handling are expected to write a function which has the same
diff --git a/pngrtran.c b/pngrtran.c
index 092e6f8..2db8ec6 100644
--- a/pngrtran.c
+++ b/pngrtran.c
@@ -1,12 +1,12 @@
/* pngrtran.c - transforms the data in a row for PNG readers
*
- * libpng 0.99c
+ * libpng 0.99d
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
- * February 7, 1998
+ * February 8, 1998
*
* This file contains functions optionally called by an application
* in order to tell libpng how to handle data when reading a PNG.
@@ -1913,24 +1913,21 @@
{
if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
{
- int i;
png_color back;
back.red = (png_byte)png_ptr->background.red;
back.green = (png_byte)png_ptr->background.green;
back.blue = (png_byte)png_ptr->background.blue;
- for (i = 0; i < num_palette; i++)
+ for (i = 0; i < (int)png_ptr->num_trans && i < num_palette; i++)
{
- if (i >= (int)png_ptr->num_trans ||
- png_ptr->trans[i] == 0)
+ if (png_ptr->trans[i] == 0)
{
palette[i].red = back.red;
palette[i].green = back.green;
palette[i].blue = back.blue;
}
- else if (i < (int)png_ptr->num_trans ||
- png_ptr->trans[i] != 0xff)
+ else if (png_ptr->trans[i] != 0xff)
{
png_composite(palette[i].red, png_ptr->palette[i].red,
png_ptr->trans[i], back.red);
diff --git a/pngrutil.c b/pngrutil.c
index 16e7aab..8609138 100644
--- a/pngrutil.c
+++ b/pngrutil.c
@@ -6,7 +6,7 @@
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
- * February 7, 1998
+ * February 8, 1998
*
* This file contains routines which are only called from within
* libpng itself during the course of reading an image.
@@ -345,6 +345,10 @@
if (!(png_ptr->mode & PNG_HAVE_IHDR) || !(png_ptr->mode & PNG_HAVE_IDAT))
{
png_error(png_ptr, "No image in file");
+
+ /* to quiet compiler warnings about unused info_ptr */
+ if (info_ptr == NULL)
+ return;
}
png_ptr->mode |= PNG_AFTER_IDAT | PNG_HAVE_IEND;
@@ -722,7 +726,7 @@
}
else if (info_ptr != NULL && info_ptr->valid & PNG_INFO_tRNS)
{
- png_warning(png_ptr, "Duplcate tRNS chunk");
+ png_warning(png_ptr, "Duplicate tRNS chunk");
png_crc_finish(png_ptr, length);
return;
}
@@ -1022,6 +1026,7 @@
png_byte type, nparams;
png_charp buf, units, endptr;
png_charpp params;
+ png_size_t slength;
int i;
png_debug(1, "in png_handle_pCAL\n");
@@ -1044,7 +1049,8 @@
png_debug1(2, "Allocating and reading pCAL chunk data (%d bytes)\n",
length + 1);
purpose = (png_charp)png_malloc(png_ptr, length + 1);
- png_crc_read(png_ptr, (png_bytep)purpose, (png_size_t)length);
+ slength = (png_size_t)length;
+ png_crc_read(png_ptr, (png_bytep)purpose, slength);
if (png_crc_finish(png_ptr, 0))
{
@@ -1052,13 +1058,13 @@
return;
}
- purpose[length] = '\0'; /* null terminate the last string */
+ purpose[slength] = 0x00; /* null terminate the last string */
png_debug(3, "Finding end of pCAL purpose string\n");
for (buf = purpose; *buf != '\0'; buf++)
/* empty loop */;
- endptr = purpose + length;
+ endptr = purpose + slength;
/* We need to have at least 12 bytes after the purpose string
in order to get the parameter information. */
@@ -1094,7 +1100,7 @@
}
/* Empty loop to move past the units string. */
- for (buf = units; *buf != '\0'; buf++);
+ for (buf = units; *buf != 0x00; buf++);
png_debug(3, "Allocating pCAL parameters array\n");
params = (png_charpp)png_malloc(png_ptr, (png_uint_32)(nparams
@@ -1107,7 +1113,7 @@
png_debug1(3, "Reading pCAL parameter %d\n", i);
/* Empty loop to move past each paramter string */
- for (params[i] = buf; *buf != '\0' && buf <= endptr; buf++);
+ for (params[i] = buf; *buf != 0x00 && buf <= endptr; buf++);
/* Make sure we haven't run out of data yet */
if (buf > endptr)
@@ -1179,6 +1185,7 @@
png_charp key;
png_charp text;
png_uint_32 skip = 0;
+ png_size_t slength;
png_debug(1, "in png_handle_tEXt\n");
@@ -1198,7 +1205,8 @@
#endif
key = (png_charp)png_malloc(png_ptr, length + 1);
- png_crc_read(png_ptr, (png_bytep)key, (png_size_t)length);
+ slength = (png_size_t)length;
+ png_crc_read(png_ptr, (png_bytep)key, slength);
if (png_crc_finish(png_ptr, skip))
{
@@ -1206,12 +1214,12 @@
return;
}
- key[length] = '\0';
+ key[slength] = 0x00;
for (text = key; *text; text++)
/* empty loop to find end of key */ ;
- if (text != key + (png_size_t)length)
+ if (text != key + slength)
text++;
text_ptr = (png_textp)png_malloc(png_ptr, (png_uint_32)sizeof(png_text));
@@ -1235,6 +1243,7 @@
png_charp key;
png_charp text;
int comp_type = PNG_TEXT_COMPRESSION_NONE;
+ png_size_t slength;
png_debug(1, "in png_handle_zTXt\n");
@@ -1256,20 +1265,21 @@
#endif
key = (png_charp)png_malloc(png_ptr, length + 1);
- png_crc_read(png_ptr, (png_bytep)key, (png_size_t)length);
+ slength = (png_size_t)length;
+ png_crc_read(png_ptr, (png_bytep)key, slength);
if (png_crc_finish(png_ptr, 0))
{
png_free(png_ptr, key);
return;
}
- key[length] = '\0';
+ key[slength] = 0x00;
for (text = key; *text; text++)
/* empty loop */ ;
/* zTXt must have some text after the keyword */
- if (text == key + (png_size_t)length)
+ if (text == key + slength)
{
png_warning(png_ptr, "Zero length zTXt chunk");
}
@@ -1283,7 +1293,7 @@
png_ptr->zstream.next_out = png_ptr->zbuf;
png_ptr->zstream.avail_out = png_ptr->zbuf_size;
- key_size = text - key;
+ key_size = (png_size_t)(text - key);
text_size = 0;
text = NULL;
@@ -1308,10 +1318,10 @@
png_memcpy(text, key, key_size);
}
- text[text_size - 1] = '\0';
+ text[text_size - 1] = 0x00;
/* Copy what we can of the error message into the text chunk */
- text_size = (png_size_t)length - (text - key) - 1;
+ text_size = (png_size_t)(slength - (text - key) - 1);
text_size = sizeof(msg) > text_size ? text_size : sizeof(msg);
png_memcpy(text + key_size, msg, text_size + 1);
break;
@@ -1328,7 +1338,7 @@
png_memcpy(text, key, key_size);
text_size = key_size + png_ptr->zbuf_size -
png_ptr->zstream.avail_out;
- *(text + text_size) = '\0';
+ *(text + text_size) = 0x00;
}
else
{
@@ -1342,7 +1352,7 @@
png_memcpy(text + text_size, png_ptr->zbuf,
(png_ptr->zbuf_size - png_ptr->zstream.avail_out));
text_size += png_ptr->zbuf_size - png_ptr->zstream.avail_out;
- *(text + text_size) = '\0';
+ *(text + text_size) = 0x00;
}
if (ret != Z_STREAM_END)
{
@@ -1376,7 +1386,7 @@
#endif
/* Copy what we can of the error message into the text chunk */
- text_size = (png_size_t)length - (text - key) - 1;
+ text_size = (png_size_t)(slength - (text - key) - 1);
text_size = sizeof(msg) > text_size ? text_size : sizeof(msg);
png_memcpy(text, msg, text_size + 1);
}
@@ -1409,12 +1419,17 @@
if (!(png_ptr->chunk_name[0] & 0x20))
{
png_chunk_error(png_ptr, "unknown critical chunk");
+ /* to quiet compiler warnings about unused info_ptr */
+
+ if (info_ptr == NULL)
+ return;
}
if (png_ptr->mode & PNG_HAVE_IDAT)
png_ptr->mode |= PNG_AFTER_IDAT;
png_crc_finish(png_ptr, length);
+
}
/* This function is called to verify that a chunk name is valid.
@@ -1847,8 +1862,8 @@
pixel_bytes = (row_info->pixel_depth >> 3);
- sp = row + (row_info->width - 1) * pixel_bytes;
- dp = row + (final_width - 1) * pixel_bytes;
+ sp = row + (png_size_t)(row_info->width - 1) * pixel_bytes;
+ dp = row + (png_size_t)(final_width - 1) * pixel_bytes;
for (i = row_info->width; i; i--)
{
png_byte v[8];
@@ -1993,7 +2008,7 @@
if (png_ptr->interlaced)
{
png_ptr->row_number = 0;
- png_buffered_memset(png_ptr, png_ptr->prev_row, 0, png_ptr->rowbytes + 1);
+ png_memset_check(png_ptr, png_ptr->prev_row, 0, png_ptr->rowbytes + 1);
do
{
png_ptr->pass++;
@@ -2203,7 +2218,7 @@
png_ptr->prev_row = (png_bytep)png_malloc(png_ptr, (png_uint_32)(
png_ptr->rowbytes + 1));
- png_buffered_memset(png_ptr, png_ptr->prev_row, 0, png_ptr->rowbytes + 1);
+ png_memset_check(png_ptr, png_ptr->prev_row, 0, png_ptr->rowbytes + 1);
png_debug1(3, "width = %d,\n", png_ptr->width);
png_debug1(3, "height = %d,\n", png_ptr->height);
diff --git a/pngset.c b/pngset.c
index d6db45b..c090a1c 100644
--- a/pngset.c
+++ b/pngset.c
@@ -1,12 +1,12 @@
/* pngset.c - storage of image information into info struct
*
- * libpng 0.99c
+ * libpng 0.99d
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
- * February 7, 1998
+ * February 8, 1998
*
* The functions here are used during reads to store data from the file
* into the info struct, and during writes to store application data
@@ -22,7 +22,7 @@
png_set_bKGD(png_structp png_ptr, png_infop info_ptr, png_color_16p background)
{
png_debug1(1, "in %s storage function\n", "bKGD");
- if (info_ptr == NULL)
+ if (png_ptr == NULL || info_ptr == NULL)
return;
png_memcpy(&(info_ptr->background), background, sizeof(png_color_16));
@@ -37,7 +37,7 @@
double green_x, double green_y, double blue_x, double blue_y)
{
png_debug1(1, "in %s storage function\n", "cHRM");
- if (info_ptr == NULL)
+ if (png_ptr == NULL || info_ptr == NULL)
return;
info_ptr->x_white = (float)white_x;
@@ -57,7 +57,7 @@
png_set_gAMA(png_structp png_ptr, png_infop info_ptr, double file_gamma)
{
png_debug1(1, "in %s storage function\n", "gAMA");
- if (info_ptr == NULL)
+ if (png_ptr == NULL || info_ptr == NULL)
return;
info_ptr->gamma = (float)file_gamma;
@@ -70,7 +70,7 @@
png_set_hIST(png_structp png_ptr, png_infop info_ptr, png_uint_16p hist)
{
png_debug1(1, "in %s storage function\n", "hIST");
- if (info_ptr == NULL)
+ if (png_ptr == NULL || info_ptr == NULL)
return;
info_ptr->hist = hist;
@@ -86,7 +86,7 @@
{
int rowbytes_per_pixel;
png_debug1(1, "in %s storage function\n", "IHDR");
- if (info_ptr == NULL)
+ if (png_ptr == NULL || info_ptr == NULL)
return;
info_ptr->width = width;
@@ -123,7 +123,7 @@
png_uint_32 offset_x, png_uint_32 offset_y, int unit_type)
{
png_debug1(1, "in %s storage function\n", "oFFs");
- if (info_ptr == NULL)
+ if (png_ptr == NULL || info_ptr == NULL)
return;
info_ptr->x_offset = offset_x;
@@ -140,10 +140,10 @@
png_charp units, png_charpp params)
{
png_uint_32 length;
- png_uint_32 i;
+ int i;
png_debug1(1, "in %s storage function\n", "pCAL");
- if (info_ptr == NULL)
+ if (png_ptr == NULL || info_ptr == NULL)
return;
length = png_strlen(purpose) + 1;
@@ -184,7 +184,7 @@
png_uint_32 res_x, png_uint_32 res_y, int unit_type)
{
png_debug1(1, "in %s storage function\n", "pHYs");
- if (info_ptr == NULL)
+ if (png_ptr == NULL || info_ptr == NULL)
return;
info_ptr->x_pixels_per_unit = res_x;
@@ -199,7 +199,7 @@
png_colorp palette, int num_palette)
{
png_debug1(1, "in %s storage function\n", "PLTE");
- if (info_ptr == NULL)
+ if (png_ptr == NULL || info_ptr == NULL)
return;
info_ptr->palette = palette;
@@ -213,7 +213,7 @@
png_color_8p sig_bit)
{
png_debug1(1, "in %s storage function\n", "sBIT");
- if (info_ptr == NULL)
+ if (png_ptr == NULL || info_ptr == NULL)
return;
png_memcpy(&(info_ptr->sig_bit), sig_bit, sizeof (png_color_8));
@@ -226,7 +226,7 @@
png_set_sRGB(png_structp png_ptr, png_infop info_ptr, int intent)
{
png_debug1(1, "in %s storage function\n", "sRGB");
- if (info_ptr == NULL)
+ if (png_ptr == NULL || info_ptr == NULL)
return;
info_ptr->srgb_intent = (png_byte)intent;
@@ -243,7 +243,7 @@
float white_x, white_y, red_x, red_y, green_x, green_y, blue_x, blue_y;
#endif
png_debug1(1, "in %s storage function\n", "sRGB_gAMA_and_cHRM");
- if (info_ptr == NULL)
+ if (png_ptr == NULL || info_ptr == NULL)
return;
png_set_sRGB(png_ptr, info_ptr, intent);
@@ -281,7 +281,7 @@
png_debug1(1, "in %s storage function\n", (png_ptr->chunk_name[0] == '\0' ?
"text" : (png_const_charp)png_ptr->chunk_name));
- if (info_ptr == NULL || num_text == 0)
+ if (png_ptr == NULL || info_ptr == NULL || num_text == 0)
return;
/* Make sure we have enough space in the "text" array in info_struct
@@ -298,7 +298,7 @@
info_ptr->max_text = info_ptr->num_text + num_text + 8;
old_text = info_ptr->text;
info_ptr->text = (png_textp)png_malloc(png_ptr,
- info_ptr->max_text * sizeof (png_text));
+ (png_uint_32)(info_ptr->max_text * sizeof (png_text)));
png_memcpy(info_ptr->text, old_text, (png_size_t)(old_max *
sizeof(png_text)));
png_free(png_ptr, old_text);
@@ -344,7 +344,7 @@
png_set_tIME(png_structp png_ptr, png_infop info_ptr, png_timep mod_time)
{
png_debug1(1, "in %s storage function\n", "tIME");
- if (info_ptr == NULL)
+ if (png_ptr == NULL || info_ptr == NULL)
return;
png_memcpy(&(info_ptr->mod_time), mod_time, sizeof (png_time));
@@ -358,7 +358,7 @@
png_bytep trans, int num_trans, png_color_16p trans_values)
{
png_debug1(1, "in %s storage function\n", "tRNS");
- if (info_ptr == NULL)
+ if (png_ptr == NULL || info_ptr == NULL)
return;
if (trans != NULL)
diff --git a/pngtest.c b/pngtest.c
index f57f78c..2bcb023 100644
--- a/pngtest.c
+++ b/pngtest.c
@@ -1,12 +1,12 @@
/* pngtest.c - a simple test program to test libpng
*
- * libpng 0.99c
+ * libpng 0.99d
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
- * February 7, 1998
+ * February 8, 1998
*
* This program reads in a PNG image, writes it out again, and then
* compares the two files. If the files are identical, this shows that
@@ -39,7 +39,6 @@
#ifdef PNGTEST_MEMORY_DEBUG
#include <unistd.h>
-void *sbrk (ssize_t incr);
#endif
int test_one_file(PNG_CONST char *inname, PNG_CONST char *outname);
@@ -857,7 +856,6 @@
pinfo = pinfo->next;
}
}
- fprintf(STDERR, "sbrk(0)=%d\n",sbrk(0));
#endif
}
#ifdef PNGTEST_MEMORY_DEBUG
diff --git a/pngtrans.c b/pngtrans.c
index fb993db..eabc493 100644
--- a/pngtrans.c
+++ b/pngtrans.c
@@ -1,12 +1,12 @@
/* pngtrans.c - transforms the data in a row (used by both readers and writers)
*
- * libpng 0.99c
+ * libpng 0.99d
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
- * February 7, 1998
+ * February 8, 1998
*/
#define PNG_INTERNAL
diff --git a/pngwio.c b/pngwio.c
index ec7f76f..33c118f 100644
--- a/pngwio.c
+++ b/pngwio.c
@@ -1,12 +1,12 @@
/* pngwio.c - functions for data output
*
- * libpng 0.99c
+ * libpng 0.99d
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
- * February 7, 1998
+ * February 8, 1998
*
* This file provides a location for all output. Users which need
* special handling are expected to write functions which have the same
@@ -180,7 +180,7 @@
#if defined(USE_FAR_KEYWORD)
#if defined(_MSC_VER)
-void *far_to_near(png_structp png_ptr,png_voidp ptr, int check)
+void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check)
{
void *near_ptr;
void FAR *far_ptr;
@@ -192,7 +192,7 @@
return(near_ptr);
}
# else
-void *far_to_near(png_structp png_ptr,png_voidp ptr, int check)
+void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check)
{
void *near_ptr;
void FAR *far_ptr;
diff --git a/pngwrite.c b/pngwrite.c
index 39754d4..0d2c48e 100644
--- a/pngwrite.c
+++ b/pngwrite.c
@@ -1,12 +1,12 @@
/* pngwrite.c - general routines to write a PNG file
*
- * libpng 0.99c
+ * libpng 0.99d
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
- * February 7, 1998
+ * February 8, 1998
*/
/* get internal access to png.h */
@@ -502,7 +502,7 @@
png_debug1(3, "row_info->rowbytes = %d\n", png_ptr->row_info.rowbytes);
/* Copy user's row into buffer, leaving room for filter byte. */
- png_buffered_memcpy(png_ptr, png_ptr->row_buf + 1, row,
+ png_memcpy_check(png_ptr, png_ptr->row_buf + 1, row,
png_ptr->row_info.rowbytes);
#if defined(PNG_WRITE_INTERLACING_SUPPORTED)
@@ -831,10 +831,10 @@
if (png_ptr->filter_weights == NULL)
{
- png_ptr->filter_weights = (png_uint_16p)png_malloc(png_ptr,
+ png_ptr->filter_weights = png_malloc(png_ptr,
(png_uint_32)(sizeof(png_uint_16) * num_weights));
- png_ptr->inv_filter_weights = (png_uint_16p)png_malloc(png_ptr,
+ png_ptr->inv_filter_weights = png_malloc(png_ptr,
(png_uint_32)(sizeof(png_uint_16) * num_weights));
for (i = 0; i < num_weights; i++)
@@ -866,7 +866,7 @@
*/
if (png_ptr->filter_costs == NULL)
{
- png_ptr->filter_costs = (png_uint_16p)png_malloc(png_ptr,
+ png_ptr->filter_costs = png_malloc(png_ptr,
(png_uint_32)(sizeof(png_uint_16) * PNG_FILTER_VALUE_LAST));
png_ptr->inv_filter_costs = (png_uint_16p)png_malloc(png_ptr,
diff --git a/pngwtran.c b/pngwtran.c
index b66d192..0af0263 100644
--- a/pngwtran.c
+++ b/pngwtran.c
@@ -1,12 +1,12 @@
/* pngwtran.c - transforms the data in a row for PNG writers
*
- * libpng 0.99c
+ * libpng 0.99d
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
- * February 7, 1998
+ * February 8, 1998
*/
#define PNG_INTERNAL
diff --git a/pngwutil.c b/pngwutil.c
index c1ccf19..7a5421a 100644
--- a/pngwutil.c
+++ b/pngwutil.c
@@ -1,12 +1,12 @@
/* pngwutil.c - utilities to write a PNG file
*
- * libpng 0.99c
+ * libpng 0.99d
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
- * February 7, 1998
+ * February 8, 1998
*/
#define PNG_INTERNAL
@@ -1358,7 +1358,7 @@
i += png_pass_inc[pass])
{
/* find out where the original pixel is */
- sp = row + i * pixel_bytes;
+ sp = row + (png_size_t)i * pixel_bytes;
/* move the pixel */
if (dp != sp)
png_memcpy(dp, sp, pixel_bytes);
diff --git a/synopsis.txt b/synopsis.txt
deleted file mode 100644
index 3aae42e..0000000
--- a/synopsis.txt
+++ /dev/null
@@ -1,687 +0,0 @@
-Synopsis, for man pages:
-
-void *far_to_near (png_structp png_ptr,png_voidp ptr,int
-check);
-
-png_voidp png_buffered_memcpy (png_structp png_ptr, png_voidp
-s1, png_voidp s2, png_uint_32 size);
-
-png_voidp png_buffered_memset (png_structp png_ptr, png_voidp
-s1, int value, png_uint_32 size);
-
-void png_build_gamma_table (png_structp png_ptr);
-
-void png_build_grayscale_palette (int bit_depth, png_colorp
-palette);
-
-void png_calculate_crc (png_structp png_ptr, png_bytep ptr,
-png_size_t length);
-
-void png_check_chunk_name (png_structp png_ptr, png_bytep
-chunk_name);
-
-png_size_t png_check_keyword (png_structp png_ptr, png_charp
-key, png_charpp new_key);
-
-int png_check_sig (png_bytep sig, int num);
-
-void png_chunk_error (png_structp png_ptr, png_const_charp
-error);
-
-void png_chunk_warning (png_structp png_ptr, png_const_charp
-message);
-
-void png_combine_row (png_structp png_ptr, png_bytep row, int
-mask);
-
-void png_convert_from_struct_tm (png_timep ptime, struct tm FAR
-* ttime);
-
-void png_convert_from_time_t (png_timep ptime, time_t ttime);
-
-png_charp png_convert_to_rfc1123) (png_structp png_ptr,
-png_timep ptime);
-
-void png_correct_palette (png_structp png_ptr, png_colorp
-palette, int num_palette);
-
-int png_crc_error (png_structp png_ptr);
-
-int png_crc_finish (png_structp png_ptr, png_uint_32 skip);
-
-void png_crc_read (png_structp png_ptr, png_bytep buf,
-png_size_t length);
-
-png_infop png_create_info_struct) (png_structp png_ptr);
-
-png_structp png_create_read_struct) (png_const_charp
-user_png_ver, voidp error_ptr, png_error_ptr error_fn,
-png_error_ptr warn_fn);
-
-png_voidp png_create_struct (int type);
-
-png_structp png_create_write_struct) (png_const_charp
-user_png_ver, voidp error_ptr, png_error_ptr error_fn,
-png_error_ptr warn_fn);
-
-void png_debug_free (png_structp png_ptr, png_voidp ptr);
-
-png_voidp png_debug_malloc (png_structp png_ptr, png_uint_32
-size);
-
-void png_destroy_info_struct (png_structp png_ptr, png_infopp
-info_ptr_ptr);
-
-void png_destroy_read_struct (png_structpp png_ptr_ptr,
-png_infopp info_ptr_ptr, png_infopp end_info_ptr_ptr);
-
-void png_destroy_struct (png_voidp struct_ptr);
-
-void png_destroy_write_struct (png_structpp png_ptr_ptr,
-png_infopp info_ptr_ptr);
-
-void png_do_background (png_row_infop row_info, png_bytep row,
-png_color_16p trans_values, png_color_16p background,
-png_color_16p background_1, png_bytep gamma_table, png_bytep
-gamma_from_1, png_bytep gamma_to_1, png_uint_16pp gamma_16,
-png_uint_16pp gamma_16_from_1, png_uint_16pp gamma_16_to_1, int
-gamma_shift);
-
-void png_do_bgr (png_row_infop row_info, png_bytep row);
-
-void png_do_chop (png_row_infop row_info, png_bytep row);
-
-void png_do_dither (png_row_infop row_info, png_bytep row,
-png_bytep palette_lookup, png_bytep dither_lookup);
-
-void png_do_expand (png_row_infop row_info, png_bytep row,
-png_color_16p trans_value);
-
-void png_do_expand_palette (png_row_infop row_info, png_bytep
-row, png_colorp palette, png_bytep trans, int num_trans);
-
-void png_do_gamma (png_row_infop row_info, png_bytep row,
-png_bytep gamma_table, png_uint_16pp gamma_16_table, int
-gamma_shift);
-
-void png_do_gray_to_rgb (png_row_infop row_info, png_bytep
-row);
-
-void png_do_invert (png_row_infop row_info, png_bytep row);
-
-void png_do_pack (png_row_infop row_info, png_bytep row,
-png_uint_32 bit_depth);
-
-void png_do_packswap (png_row_infop row_info, png_bytep row);
-
-void png_do_read_filler (png_row_infop row_info, png_bytep row,
-png_uint_32 filler, png_uint_32 flags);
-
-void png_do_read_interlace (png_row_infop row_info, png_bytep
-row, int pass, png_uint_32 transformations);
-
-void png_do_read_invert_alpha (png_row_infop row_info,
-png_bytep row);
-
-void png_do_read_swap_alpha (png_row_infop row_info, png_bytep
-row);
-
-void png_do_read_transformations (png_structp png_ptr);
-
-void png_do_rgb_to_gray (png_row_infop row_info, png_bytep
-row);
-
-void png_do_shift (png_row_infop row_info, png_bytep row,
-png_color_8p bit_depth);
-
-void png_do_strip_filler (png_row_infop row_info, png_bytep
-row, png_uint_32 flags);
-
-void png_do_swap (png_row_infop row_info, png_bytep row);
-
-void png_do_unpack (png_row_infop row_info, png_bytep row);
-
-void png_do_unshift (png_row_infop row_info, png_bytep row,
-png_color_8p sig_bits);
-
-void png_do_write_interlace (png_row_infop row_info, png_bytep
-row, int pass);
-
-void png_do_write_invert_alpha (png_row_infop row_info,
-png_bytep row);
-
-void png_do_write_swap_alpha (png_row_infop row_info, png_bytep
-row);
-
-void png_do_write_transformations (png_structp png_ptr);
-
-void png_error (png_structp png_ptr, png_const_charp error);
-
-void png_flush (png_structp png_ptr);
-
-void png_free (png_structp png_ptr, png_voidp ptr);
-
-png_byte png_get_bit_depth (png_structp png_ptr, png_infop
-info_ptr);
-
-png_uint_32 png_get_bKGD (png_structp png_ptr, png_infop
-info_ptr, png_color_16p *background);
-
-png_byte png_get_channels (png_structp png_ptr, png_infop
-info_ptr);
-
-png_uint_32 png_get_cHRM (png_structp png_ptr, png_infop
-info_ptr, double *white_x, double *white_y, double *red_x,
-double *red_y, double *green_x, double *green_y, double
-*blue_x, double *blue_y);
-
-png_byte png_get_color_type (png_structp png_ptr, png_infop
-info_ptr);
-
-png_byte png_get_compression_type (png_structp png_ptr,
-png_infop info_ptr);
-
-png_voidp png_get_error_ptr (png_structp png_ptr);
-
-png_byte png_get_filter_type (png_structp png_ptr, png_infop
-info_ptr);
-
-png_uint_32 png_get_gAMA (png_structp png_ptr, png_infop
-info_ptr, double *file_gamma);
-
-png_uint_32 png_get_hIST (png_structp png_ptr, png_infop
-info_ptr, png_uint_16p *hist);
-
-png_uint_32 png_get_image_height (png_structp png_ptr,
-png_infop info_ptr);
-
-png_uint_32 png_get_image_width (png_structp png_ptr, png_infop
-info_ptr);
-
-png_int_32 png_get_int_32 (png_bytep buf);
-
-png_byte png_get_interlace_type (png_structp png_ptr, png_infop
-info_ptr);
-
-png_voidp png_get_io_ptr (png_structp png_ptr);
-
-png_uint_32 png_get_IHDR (png_structp png_ptr, png_infop
-info_ptr, png_uint_32 *width, png_uint_32 *height, int
-*bit_depth, int *color_type, int *interlace_type, int
-*compression_type, int *filter_type);
-
-png_uint_32 png_get_oFFs (png_structp png_ptr, png_infop
-info_ptr, png_uint_32 *offset_x, png_uint_32 *offset_y, int
-*unit_type);
-
-png_uint_32 png_get_pCAL (png_structp png_ptr, png_infop
-info_ptr, png_charp *purpose, png_int_32 *X0, png_int_32 *X1,
-int *type, int *nparams, png_charp *units, png_charpp *params);
-
-png_uint_32 png_get_pHYs (png_structp png_ptr, png_infop
-info_ptr, png_uint_32 *res_x, png_uint_32 *res_y, int
-*unit_type);
-
-float png_get_pixel_aspect_ratio (png_structp png_ptr,
-png_infop info_ptr);
-
-png_uint_32 png_get_pixels_per_meter (png_structp png_ptr,
-png_infop info_ptr);
-
-png_voidp png_get_progressive_ptr (png_structp png_ptr);
-
-png_uint_32 png_get_PLTE (png_structp png_ptr, png_infop
-info_ptr, png_colorp *palette, int *num_palette);
-
-png_uint_32 png_get_rowbytes (png_structp png_ptr, png_infop
-info_ptr);
-
-png_uint_32 png_get_sBIT (png_structp png_ptr, png_infop
-info_ptr, png_color_8p *sig_bit);
-
-png_bytep png_get_signature (png_structp png_ptr, png_infop
-info_ptr);
-
-png_uint_32 png_get_sRGB (png_structp png_ptr, png_infop
-info_ptr, int *intent);
-
-png_uint_32 png_get_text (png_structp png_ptr, png_infop
-info_ptr, png_textp *text_ptr, int *num_text);
-
-png_uint_32 png_get_tIME (png_structp png_ptr, png_infop
-info_ptr, png_timep *mod_time);
-
-png_uint_32 png_get_tRNS (png_structp png_ptr, png_infop
-info_ptr, png_bytep *trans, int *num_trans, png_color_16p
-*trans_values);
-
-png_uint_16 png_get_uint_16 (png_bytep buf);
-
-png_uint_32 png_get_uint_32 (png_bytep buf);
-
-png_uint_32 png_get_valid (png_structp png_ptr, png_infop
-info_ptr, png_uint_32 flag);
-
-png_uint_32 png_get_x_offset_microns (png_structp png_ptr,
-png_infop info_ptr);
-
-png_uint_32 png_get_x_offset_pixels (png_structp png_ptr,
-png_infop info_ptr);
-
-png_uint_32 png_get_y_offset_microns (png_structp png_ptr,
-png_infop info_ptr);
-
-png_uint_32 png_get_y_offset_pixels (png_structp png_ptr,
-png_infop info_ptr);
-
-void png_handle_bKGD (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 length);
-
-void png_handle_cHRM (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 length);
-
-void png_handle_gAMA (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 length);
-
-void png_handle_hIST (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 length);
-
-void png_handle_IEND (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 length);
-
-void png_handle_IHDR (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 length);
-
-void png_handle_oFFs (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 length);
-
-void png_handle_pCAL (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 length);
-
-void png_handle_pHYs (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 length);
-
-void png_handle_PLTE (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 length);
-
-void png_handle_sBIT (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 length);
-
-void png_handle_sRGB (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 length);
-
-void png_handle_tEXt (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 length);
-
-void png_handle_tIME (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 length);
-
-void png_handle_tRNS (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 length);
-
-void png_handle_unknown (png_structp png_ptr, png_infop
-info_ptr, png_uint_32 length);
-
-void png_handle_zTXt (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 length);
-
-void png_info_destroy (png_structp png_ptr, png_infop
-info_ptr);
-
-void png_info_init (png_infop info_ptr);
-
-void png_init_io (png_structp png_ptr, FILE *fp);
-
-void png_init_read_transformations (png_structp png_ptr);
-
-png_voidp png_malloc (png_structp png_ptr, png_uint_32 size);
-
-void png_process_data (png_structp png_ptr, png_infop info_ptr,
-png_bytep buffer, png_size_t buffer_size);
-
-void png_process_IDAT_data (png_structp png_ptr, png_bytep
-buffer, png_size_t buffer_length);
-
-void png_process_some_data (png_structp png_ptr, png_infop
-info_ptr);
-
-void png_progressive_combine_row (png_structp png_ptr,
-png_bytep old_row, png_bytep new_row);
-
-void png_push_check_crc (png_structp png_ptr);
-
-void png_push_crc_finish (png_structp png_ptr);
-
-void png_push_crc_skip (png_structp png_ptr, png_uint_32
-length);
-
-void png_push_fill_buffer (png_structp png_ptr, png_bytep
-buffer, png_size_t length);
-
-void png_push_handle_tEXt (png_structp png_ptr, png_infop
-info_ptr, png_uint_32 length);
-
-void png_push_handle_unknown (png_structp png_ptr, png_infop
-info_ptr, png_uint_32 length);
-
-void png_push_handle_zTXt (png_structp png_ptr, png_infop
-info_ptr, png_uint_32 length);
-
-void png_push_have_end (png_structp png_ptr, png_infop
-info_ptr);
-
-void png_push_have_info (png_structp png_ptr, png_infop
-info_ptr);
-
-void png_push_have_row (png_structp png_ptr, png_bytep row);
-
-void png_push_process_row (png_structp png_ptr);
-
-void png_push_read_chunk (png_structp png_ptr, png_infop
-info_ptr);
-
-void png_push_read_end (png_structp png_ptr, png_infop
-info_ptr);
-
-void png_push_read_IDAT (png_structp png_ptr);
-
-void png_push_read_sig (png_structp png_ptr, png_infop
-info_ptr);
-
-void png_push_read_tEXt (png_structp png_ptr, png_infop
-info_ptr);
-
-void png_push_read_zTXt (png_structp png_ptr, png_infop
-info_ptr);
-
-void png_push_restore_buffer (png_structp png_ptr, png_bytep
-buffer, png_size_t buffer_length);
-
-void png_push_save_buffer (png_structp png_ptr);
-
-void png_read_data (png_structp png_ptr, png_bytep data,
-png_size_t length);
-
-void png_read_destroy (png_structp png_ptr, png_infop info_ptr,
-png_infop end_info_ptr);
-
-void png_read_end (png_structp png_ptr, png_infop info_ptr);
-
-void png_read_filter_row (png_structp png_ptr, png_row_infop
-row_info, png_bytep row, png_bytep prev_row, int filter);
-
-void png_read_finish_row (png_structp png_ptr);
-
-void png_read_image (png_structp png_ptr, png_bytepp image);
-
-void png_read_info (png_structp png_ptr, png_infop info_ptr);
-
-void png_read_init (png_structp png_ptr);
-
-void png_read_push_finish_row (png_structp png_ptr);
-
-void png_read_row (png_structp png_ptr, png_bytep row,
-png_bytep display_row);
-
-void png_read_rows (png_structp png_ptr, png_bytepp row,
-png_bytepp display_row, png_uint_32 num_rows);
-
-void png_read_start_row (png_structp png_ptr);
-
-void png_read_transform_info (png_structp png_ptr, png_infop
-info_ptr);
-
-void png_read_update_info (png_structp png_ptr, png_infop
-info_ptr);
-
-void png_reset_crc (png_structp png_ptr);
-
-void png_save_int_32 (png_bytep buf, png_int_32 i);
-
-void png_save_uint_16 (png_bytep buf, unsigned int i);
-
-void png_save_uint_32 (png_bytep buf, png_uint_32 i);
-
-void png_set_background (png_structp png_ptr, png_color_16p
-background_color, int background_gamma_code, int need_expand,
-double background_gamma);
-
-void png_set_bgr (png_structp png_ptr);
-
-void png_set_bKGD (png_structp png_ptr, png_infop info_ptr,
-png_color_16p background);
-
-void png_set_cHRM (png_structp png_ptr, png_infop info_ptr,
-double white_x, double white_y, double red_x, double red_y,
-double green_x, double green_y, double blue_x, double blue_y);
-
-void png_set_compression_level (png_structp png_ptr, int
-level);
-
-void png_set_compression_mem_level) (png_structp png_ptr, int
-mem_level);
-
-void png_set_compression_method (png_structp png_ptr, int
-method);
-
-void png_set_compression_strategy) (png_structp png_ptr, int
-strategy);
-
-void png_set_compression_window_bits) (png_structp png_ptr, int
-window_bits);
-
-void png_set_crc_action (png_structp png_ptr, int crit_action,
-int ancil_action);
-
-void png_set_dither (png_structp png_ptr, png_colorp palette,
-int num_palette, int maximum_colors, png_uint_16p histogram,
-int full_dither);
-
-void png_set_error_fn (png_structp png_ptr, png_voidp
-error_ptr, png_error_ptr error_fn, png_error_ptr warning_fn);
-
-void png_set_expand (png_structp png_ptr);
-
-void png_set_filler (png_structp png_ptr, png_uint_32 filler,
-int flags);
-
-void png_set_filter (png_structp png_ptr, int method, int
-filters);
-
-void png_set_filter_heuristics (png_structp png_ptr, int
-heuristic_method, int num_weights, png_doublep filter_weights,
-png_doublep filter_costs);
-
-void png_set_flush (png_structp png_ptr, int nrows);
-
-void png_set_gamma (png_structp png_ptr, double screen_gamma,
-double default_file_gamma);
-
-void png_set_gAMA (png_structp png_ptr, png_infop info_ptr,
-double file_gamma);
-
-void png_set_gray_to_rgb (png_structp png_ptr);
-
-void png_set_hIST (png_structp png_ptr, png_infop info_ptr,
-png_uint_16p hist);
-
-int png_set_interlace_handling (png_structp png_ptr);
-
-void png_set_invert_alpha (png_structp png_ptr);
-
-void png_set_invert_mono (png_structp png_ptr);
-
-void png_set_IHDR (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 width, png_uint_32 height, int bit_depth, int
-color_type, int interlace_type, int compression_type, int
-filter_type);
-
-void png_set_oFFs (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 offset_x, png_uint_32 offset_y, int unit_type);
-
-void png_set_packing (png_structp png_ptr);
-
-void png_set_packswap (png_structp png_ptr);
-
-void png_set_pCAL (png_structp png_ptr, png_infop info_ptr,
-png_charp purpose, png_int_32 X0, png_int_32 X1, int type, int
-nparams, png_charp units, png_charpp params);
-
-void png_set_pHYs (png_structp png_ptr, png_infop info_ptr,
-png_uint_32 res_x, png_uint_32 res_y, int unit_type);
-
-void png_set_progressive_read_fn (png_structp png_ptr,
-png_voidp progressive_ptr, png_progressive_info_ptr info_fn,
-png_progressive_row_ptr row_fn, png_progressive_end_ptr
-end_fn);
-
-void png_set_PLTE (png_structp png_ptr, png_infop info_ptr,
-png_colorp palette, int num_palette);
-
-void png_set_read_fn (png_structp png_ptr, png_voidp io_ptr,
-png_rw_ptr read_data_fn);
-
-void png_set_rgb_to_gray (png_structp png_ptr);
-
-void png_set_sBIT (png_structp png_ptr, png_infop info_ptr,
-png_color_8p sig_bit);
-
-void png_set_shift (png_structp png_ptr, png_color_8p
-true_bits);
-
-void png_set_sig_bytes (png_structp png_ptr, int num_bytes);
-
-void png_set_sRGB (png_structp png_ptr, png_infop info_ptr, int
-intent);
-
-void png_set_sRGB_gAMA_and_cHRM (png_structp png_ptr, png_infop
-info_ptr, int intent);
-
-void png_set_strip_16 (png_structp png_ptr);
-
-void png_set_strip_alpha (png_structp png_ptr);
-
-void png_set_swap (png_structp png_ptr);
-
-void png_set_swap_alpha (png_structp png_ptr);
-
-void png_set_text (png_structp png_ptr, png_infop info_ptr,
-png_textp text_ptr, int num_text);
-
-void png_set_tIME (png_structp png_ptr, png_infop info_ptr,
-png_timep mod_time);
-
-void png_set_tRNS (png_structp png_ptr, png_infop info_ptr,
-png_bytep trans, int num_trans, png_color_16p trans_values);
-
-void png_set_write_fn (png_structp png_ptr, png_voidp io_ptr,
-png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn);
-
-int png_sig_cmp (png_bytep sig, png_size_t start, png_size_t
-num_to_check);
-
-void png_start_read_image (png_structp png_ptr);
-
-void png_warning (png_structp png_ptr, png_const_charp
-message);
-
-void png_write_bKGD (png_structp png_ptr, png_color_16p values,
-int color_type);
-
-void png_write_chunk (png_structp png_ptr, png_bytep
-chunk_name, png_bytep data, png_size_t length);
-
-void png_write_chunk_data (png_structp png_ptr, png_bytep data,
-png_size_t length);
-
-void png_write_chunk_end (png_structp png_ptr);
-
-void png_write_chunk_start (png_structp png_ptr, png_bytep
-chunk_name, png_uint_32 length);
-
-void png_write_cHRM (png_structp png_ptr, double white_x,
-double white_y, double red_x, double red_y, double green_x,
-double green_y, double blue_x, double blue_y);
-
-void png_write_data (png_structp png_ptr, png_bytep data,
-png_size_t length);
-
-void png_write_destroy (png_structp png_ptr);
-
-void png_write_destroy_info (png_infop info_ptr);
-
-void png_write_end (png_structp png_ptr, png_infop info_ptr);
-
-void png_write_filtered_row (png_structp png_ptr, png_bytep
-filtered_row);
-
-void png_write_find_filter (png_structp png_ptr, png_row_infop
-row_info);
-
-void png_write_finish_row (png_structp png_ptr);
-
-void png_write_flush (png_structp png_ptr);
-
-void png_write_gAMA (png_structp png_ptr, double file_gamma);
-
-void png_write_hIST (png_structp png_ptr, png_uint_16p hist,
-int num_hist);
-
-void png_write_image (png_structp png_ptr, png_bytepp image);
-
-void png_write_info (png_structp png_ptr, png_infop info_ptr);
-
-void png_write_init (png_structp png_ptr);
-
-void png_write_IDAT (png_structp png_ptr, png_bytep data,
-png_size_t length);
-
-void png_write_IEND (png_structp png_ptr);
-
-void png_write_IHDR (png_structp png_ptr, png_uint_32 width,
-png_uint_32 height, int bit_depth, int color_type, int
-compression_type, int filter_type, int interlace_type);
-
-void png_write_oFFs (png_structp png_ptr, png_uint_32 x_offset,
-png_uint_32 y_offset, int unit_type);
-
-void png_write_pCAL (png_structp png_ptr, png_charp purpose,
-png_int_32 X0, png_int_32 X1, int type, int nparams, png_charp
-units, png_charpp params);
-
-void png_write_pHYs (png_structp png_ptr, png_uint_32
-x_pixels_per_unit, png_uint_32 y_pixels_per_unit, int
-unit_type);
-
-void png_write_PLTE (png_structp png_ptr, png_colorp palette,
-png_uint_32 num_pal);
-
-void png_write_row (png_structp png_ptr, png_bytep row);
-
-void png_write_rows (png_structp png_ptr, png_bytepp row,
-png_uint_32 num_rows);
-
-void png_write_sBIT (png_structp png_ptr, png_color_8p sbit,
-int color_type);
-
-void png_write_sig (png_structp png_ptr);
-
-void png_write_sRGB (png_structp png_ptr, int intent);
-
-void png_write_start_row (png_structp png_ptr);
-
-void png_write_tEXt (png_structp png_ptr, png_charp key,
-png_charp text, png_size_t text_len);
-
-void png_write_tIME (png_structp png_ptr, png_timep mod_time);
-
-void png_write_tRNS (png_structp png_ptr, png_bytep trans,
-png_color_16p values, int number, int color_type);
-
-void png_write_zTXt (png_structp png_ptr, png_charp key,
-png_charp text, png_size_t text_len, int compression);
-
-voidpf png_zalloc (voidpf png_ptr, uInt items, uInt size);
-
-void png_zfree (voidpf png_ptr, voidpf ptr);
-
