| |
| /* png.c - location for general purpose png functions |
| |
| libpng 1.0 beta 6 - version 0.96 |
| 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 |
| May 12, 1997 |
| */ |
| |
| #define PNG_INTERNAL |
| #define PNG_NO_EXTERN |
| #include "png.h" |
| |
| /* Version information for C files. This had better match the version |
| string defined in png.h */ |
| char png_libpng_ver[] = "0.95"; |
| |
| /* Place to hold the signiture string for a PNG file. */ |
| png_byte FARDATA png_sig[8] = {137, 80, 78, 71, 13, 10, 26, 10}; |
| |
| /* constant strings for known chunk types. If you need to add a chunk, |
| add a string holding the name here. If you want to make the code |
| portable to EBCDIC machines, use ASCII numbers, not characters. */ |
| png_byte FARDATA png_IHDR[5] = { 73, 72, 68, 82, '\0'}; |
| png_byte FARDATA png_IDAT[5] = { 73, 68, 65, 84, '\0'}; |
| png_byte FARDATA png_IEND[5] = { 73, 69, 78, 68, '\0'}; |
| png_byte FARDATA png_PLTE[5] = { 80, 76, 84, 69, '\0'}; |
| png_byte FARDATA png_bKGD[5] = { 98, 75, 71, 68, '\0'}; |
| png_byte FARDATA png_cHRM[5] = { 99, 72, 82, 77, '\0'}; |
| png_byte FARDATA png_gAMA[5] = {103, 65, 77, 65, '\0'}; |
| png_byte FARDATA png_hIST[5] = {104, 73, 83, 84, '\0'}; |
| png_byte FARDATA png_oFFs[5] = {111, 70, 70, 115, '\0'}; |
| png_byte FARDATA png_pCAL[5] = {112, 67, 65, 76, '\0'}; |
| png_byte FARDATA png_pHYs[5] = {112, 72, 89, 115, '\0'}; |
| png_byte FARDATA png_sBIT[5] = {115, 66, 73, 84, '\0'}; |
| png_byte FARDATA png_tEXt[5] = {116, 69, 88, 116, '\0'}; |
| png_byte FARDATA png_tIME[5] = {116, 73, 77, 69, '\0'}; |
| png_byte FARDATA png_tRNS[5] = {116, 82, 78, 83, '\0'}; |
| png_byte FARDATA png_zTXt[5] = {122, 84, 88, 116, '\0'}; |
| |
| /* arrays to facilitate easy interlacing - use pass (0 - 6) as index */ |
| |
| /* start of interlace block */ |
| int FARDATA png_pass_start[] = {0, 4, 0, 2, 0, 1, 0}; |
| |
| /* offset to next interlace block */ |
| int FARDATA png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1}; |
| |
| /* start of interlace block in the y direction */ |
| int FARDATA png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1}; |
| |
| /* offset to next interlace block in the y direction */ |
| int FARDATA png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2}; |
| |
| /* width of interlace block */ |
| /* this is not currently used - if you need it, uncomment it here and |
| in png.h |
| int FARDATA png_pass_width[] = {8, 4, 4, 2, 2, 1, 1}; |
| */ |
| |
| /* height of interlace block */ |
| /* this is not currently used - if you need it, uncomment it here and |
| in png.h |
| int FARDATA png_pass_height[] = {8, 8, 4, 4, 2, 2, 1}; |
| */ |
| |
| /* mask to determine which pixels are valid in a pass */ |
| int FARDATA png_pass_mask[] = {0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, 0xff}; |
| |
| /* mask to determine which pixels to overwrite while displaying */ |
| int FARDATA png_pass_dsp_mask[] = {0xff, 0x0f, 0xff, 0x33, 0xff, 0x55, 0xff}; |
| |
| |
| /* Tells libpng that we have already handled the first "num_bytes" bytes |
| * of the PNG file signature. If the PNG data is embedded into another |
| * stream we can set num_bytes = 8 so that libpng will not attempt to read |
| * or write any of the magic bytes before it starts on the IHDR. |
| */ |
| void |
| png_set_sig_bytes(png_structp png_ptr, int num_bytes) |
| { |
| png_debug(1, "in png_set_sig_bytes\n"); |
| if (num_bytes > 8) |
| png_error(png_ptr, "Too many bytes for PNG signature."); |
| |
| png_ptr->sig_bytes = num_bytes < 0 ? 0 : num_bytes; |
| } |
| |
| /* Checks whether the supplied bytes match the PNG signature. We allow |
| * checking less than the full 8-byte signature so that those apps that |
| * already read the first few bytes of a file to determine the file type |
| * can simply check the remaining bytes for extra assurance. Returns |
| * an integer less than, equal to, or greater than zero if sig is found, |
| * respectively, to be less than, to match, or be greater than the correct |
| * PNG signature (this is the same behaviour as strcmp, memcmp, etc). |
| */ |
| int |
| png_sig_cmp(png_bytep sig, png_size_t start, png_size_t num_to_check) |
| { |
| if (num_to_check > 8) |
| num_to_check = 8; |
| else if (num_to_check < 1) |
| return 0; |
| |
| if (start > 7) |
| return 0; |
| |
| if (start + num_to_check > 8) |
| num_to_check = 8 - start; |
| |
| return (png_memcmp(&sig[start], &png_sig[start], num_to_check)); |
| } |
| |
| /* (Obsolete) function to check signature bytes. It does not allow one |
| to check a partial signature. This function will be removed in the |
| future - use png_sig_cmp(). */ |
| int |
| png_check_sig(png_bytep sig, int num) |
| { |
| return !png_sig_cmp(sig, (png_size_t)0, (png_size_t)num); |
| } |
| |
| /* Function to allocate memory for zlib. */ |
| voidpf |
| png_zalloc(voidpf png_ptr, uInt items, uInt size) |
| { |
| png_voidp ptr; |
| png_uint_32 num_bytes; |
| |
| num_bytes = (png_uint_32)items * size; |
| ptr = png_malloc((png_structp)png_ptr, num_bytes); |
| if (num_bytes > (png_uint_32)0x8000) |
| { |
| png_memset(ptr, 0, (png_size_t)0x8000L); |
| png_memset((png_bytep)ptr + (png_size_t)0x8000L, 0, |
| (png_size_t)(num_bytes - (png_uint_32)0x8000L)); |
| } |
| else |
| { |
| png_memset(ptr, 0, (png_size_t)num_bytes); |
| } |
| return (voidpf)(ptr); |
| } |
| |
| /* function to free memory for zlib */ |
| void |
| png_zfree(voidpf png_ptr, voidpf ptr) |
| { |
| png_free((png_structp)png_ptr, (png_voidp)ptr); |
| } |
| |
| /* Reset the CRC variable to 32 bits of 1's. Care must be taken |
| in case CRC is > 32 bits to leave the top bits 0. */ |
| void |
| png_reset_crc(png_structp png_ptr) |
| { |
| /* set CRC to all 1's */ |
| #ifdef PNG_USE_OWN_CRC |
| png_ptr->crc = 0xffffffffL; |
| #else |
| png_ptr->crc = crc32(0, Z_NULL, 0); |
| #endif |
| } |
| |
| #ifdef PNG_USE_OWN_CRC |
| /* Table of CRCs of all 8-bit messages. By default, we use the tables made |
| by zlib, to save some memory. If you wish to png_malloc() this |
| table, turn this into a pointer, and png_malloc() it in make_crc_table(). |
| You may then want to hook it into png_struct and free it with the |
| destroy functions. Another alternative is to pre-fill the table. */ |
| static png_uint_32 crc_table[256]; |
| |
| /* Flag: has the table been computed? Initially false. */ |
| static int crc_table_computed = 0; |
| |
| /* make the table for a fast crc */ |
| static void |
| make_crc_table(void) |
| { |
| png_uint_32 c; |
| int n, k; |
| |
| for (n = 0; n < 256; n++) |
| { |
| c = (png_uint_32)n; |
| for (k = 0; k < 8; k++) |
| c = c & 1 ? 0xedb88320L ^ (c >> 1) : c >> 1; |
| crc_table[n] = c; |
| } |
| crc_table_computed = 1; |
| } |
| |
| /* Update a running CRC with the bytes buf[0..len-1] - the CRC should be |
| initialized to all 1's, and the transmitted value is the 1's complement |
| of the final running CRC. */ |
| static png_uint_32 |
| update_crc(png_uint_32 crc, png_bytep buf, png_size_t len) |
| { |
| png_uint_32 c; |
| png_bytep p; |
| png_uint_32 n; |
| |
| c = crc; |
| p = buf; |
| n = len; |
| |
| if (!crc_table_computed) |
| { |
| make_crc_table(); |
| } |
| |
| if (n > 0) do |
| { |
| c = crc_table[(png_byte)((c ^ (*p++)) & 0xff)] ^ (c >> 8); |
| } while (--n); |
| |
| return c; |
| } |
| #endif /* PNG_USE_OWN_CRC */ |
| |
| /* Calculate the CRC over a section of data. We can only pass as |
| much data to this routine as the largest single buffer size. We |
| also check that this data will actually be used before going to the |
| trouble of calculating it. */ |
| void |
| png_calculate_crc(png_structp png_ptr, png_bytep ptr, png_size_t length) |
| { |
| int need_crc = 1; |
| |
| if (png_ptr->chunk_name[0] & 0x20) /* ancillary */ |
| { |
| if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) == |
| (PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN)) |
| need_crc = 0; |
| } |
| else /* critical */ |
| { |
| if (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE) |
| need_crc = 0; |
| } |
| |
| if (need_crc) |
| #ifdef PNG_USE_OWN_CRC |
| png_ptr->crc = update_crc(png_ptr->crc, ptr, length); |
| #else |
| png_ptr->crc = crc32(png_ptr->crc, ptr, length); |
| #endif |
| } |
| |
| /* Allocate the memory for an info_struct for the application. We don't |
| really need the png_ptr, but it could potentially be useful in the |
| future. This should be used in favour of malloc(sizeof(png_info)) |
| and png_info_init() so that applications that want to use a shared |
| libpng don't have to be recompiled if png_info changes size. */ |
| png_infop |
| png_create_info_struct(png_structp png_ptr) |
| { |
| png_infop info_ptr; |
| |
| png_debug(1, "in png_create_info_struct\n"); |
| if ((info_ptr = (png_infop)png_create_struct(PNG_STRUCT_INFO)) != NULL) |
| { |
| png_info_init(info_ptr); |
| } |
| |
| return info_ptr; |
| } |
| |
| /* This function frees the memory associated with a single info struct. |
| Normally, one would use either png_destroy_read_struct() or |
| png_destroy_write_struct() to free an info struct, but this may be |
| useful for some applications. */ |
| void |
| png_destroy_info_struct(png_structp png_ptr, png_infopp info_ptr_ptr) |
| { |
| png_infop info_ptr = NULL; |
| |
| png_debug(1, "in png_destroy_info_struct\n"); |
| if (info_ptr_ptr != NULL) |
| info_ptr = *info_ptr_ptr; |
| |
| if (info_ptr != NULL) |
| { |
| png_info_destroy(png_ptr, info_ptr); |
| |
| png_destroy_struct((png_voidp)info_ptr); |
| *info_ptr_ptr = (png_infop)NULL; |
| } |
| } |
| |
| /* Initialize the info structure. This is now an internal function (0.89) |
| and applications using it are urged to use png_create_info_struct() |
| instead. */ |
| void |
| png_info_init(png_infop info_ptr) |
| { |
| png_debug(1, "in png_info_init\n"); |
| /* set everything to 0 */ |
| png_memset(info_ptr, 0, sizeof (png_info)); |
| } |
| |
| /* This is an internal routine to free any memory that the info struct is |
| * pointing to before re-using it or freeing the struct itself. Recall |
| * that png_free() checks for NULL pointers for us. |
| */ |
| void |
| png_info_destroy(png_structp png_ptr, png_infop info_ptr) |
| { |
| #if defined(PNG_READ_tEXt_SUPPORTED) || defined(PNG_READ_zTXt_SUPPORTED) |
| int i; |
| |
| png_debug(1, "in png_info_destroy\n"); |
| if (info_ptr->text != NULL) |
| { |
| for (i = 0; i < info_ptr->num_text; i++) |
| { |
| png_free(png_ptr, info_ptr->text[i].key); |
| } |
| png_free(png_ptr, info_ptr->text); |
| } |
| #endif |
| #if defined(PNG_READ_pCAL_SUPPORTED) |
| png_free(png_ptr, info_ptr->pcal_purpose); |
| png_free(png_ptr, info_ptr->pcal_units); |
| if (info_ptr->pcal_params != NULL) |
| { |
| for (i = 0; i < info_ptr->pcal_nparams; i++) |
| { |
| png_free(png_ptr, info_ptr->pcal_params[i]); |
| } |
| png_free(png_ptr, info_ptr->pcal_params); |
| } |
| #endif |
| |
| png_info_init(info_ptr); |
| } |
| |
| /* This function returns a pointer to the io_ptr associated with the user |
| functions. The application should free any memory associated with this |
| pointer before png_write_destroy() or png_read_destroy() are called. */ |
| png_voidp |
| png_get_io_ptr(png_structp png_ptr) |
| { |
| return png_ptr->io_ptr; |
| } |
| |
| #if !defined(PNG_NO_STDIO) |
| /* Initialize the default input/output functions for the PNG file. If you |
| use your own read or write routines, you can call either png_set_read_fn() |
| or png_set_write_fn() instead of png_init_io(). */ |
| void |
| png_init_io(png_structp png_ptr, FILE *fp) |
| { |
| png_debug(1, "in png_init_io\n"); |
| png_ptr->io_ptr = (png_voidp)fp; |
| } |
| #endif |