| /* |
| * wrgif.c |
| * |
| * This file was part of the Independent JPEG Group's software: |
| * Copyright (C) 1991-1997, Thomas G. Lane. |
| * Modified 2015-2019 by Guido Vollbeding. |
| * libjpeg-turbo Modifications: |
| * Copyright (C) 2015, 2017, 2022, D. R. Commander. |
| * For conditions of distribution and use, see the accompanying README.ijg |
| * file. |
| * |
| * This file contains routines to write output images in GIF format. |
| * |
| * These routines may need modification for non-Unix environments or |
| * specialized applications. As they stand, they assume output to |
| * an ordinary stdio stream. |
| */ |
| |
| /* |
| * This code is loosely based on ppmtogif from the PBMPLUS distribution |
| * of Feb. 1991. That file contains the following copyright notice: |
| * Based on GIFENCODE by David Rowley <mgardi@watdscu.waterloo.edu>. |
| * Lempel-Ziv compression based on "compress" by Spencer W. Thomas et al. |
| * Copyright (C) 1989 by Jef Poskanzer. |
| * Permission to use, copy, modify, and distribute this software and its |
| * documentation for any purpose and without fee is hereby granted, provided |
| * that the above copyright notice appear in all copies and that both that |
| * copyright notice and this permission notice appear in supporting |
| * documentation. This software is provided "as is" without express or |
| * implied warranty. |
| */ |
| |
| #include "cdjpeg.h" /* Common decls for cjpeg/djpeg applications */ |
| |
| #ifdef GIF_SUPPORTED |
| |
| |
| #define MAX_LZW_BITS 12 /* maximum LZW code size (4096 symbols) */ |
| |
| typedef INT16 code_int; /* must hold -1 .. 2**MAX_LZW_BITS */ |
| |
| #define LZW_TABLE_SIZE ((code_int)1 << MAX_LZW_BITS) |
| |
| #define HSIZE 5003 /* hash table size for 80% occupancy */ |
| |
| typedef int hash_int; /* must hold -2*HSIZE..2*HSIZE */ |
| |
| #define MAXCODE(n_bits) (((code_int)1 << (n_bits)) - 1) |
| |
| |
| /* |
| * The LZW hash table consists of two parallel arrays: |
| * hash_code[i] code of symbol in slot i, or 0 if empty slot |
| * hash_value[i] symbol's value; undefined if empty slot |
| * where slot values (i) range from 0 to HSIZE-1. The symbol value is |
| * its prefix symbol's code concatenated with its suffix character. |
| * |
| * Algorithm: use open addressing double hashing (no chaining) on the |
| * prefix code / suffix character combination. We do a variant of Knuth's |
| * algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime |
| * secondary probe. |
| */ |
| |
| typedef int hash_entry; /* must hold (code_int << 8) | byte */ |
| |
| #define HASH_ENTRY(prefix, suffix) ((((hash_entry)(prefix)) << 8) | (suffix)) |
| |
| |
| /* Private version of data destination object */ |
| |
| typedef struct { |
| struct djpeg_dest_struct pub; /* public fields */ |
| |
| j_decompress_ptr cinfo; /* back link saves passing separate parm */ |
| |
| /* State for packing variable-width codes into a bitstream */ |
| int n_bits; /* current number of bits/code */ |
| code_int maxcode; /* maximum code, given n_bits */ |
| int init_bits; /* initial n_bits ... restored after clear */ |
| int cur_accum; /* holds bits not yet output */ |
| int cur_bits; /* # of bits in cur_accum */ |
| |
| /* LZW string construction */ |
| code_int waiting_code; /* symbol not yet output; may be extendable */ |
| boolean first_byte; /* if TRUE, waiting_code is not valid */ |
| |
| /* State for GIF code assignment */ |
| code_int ClearCode; /* clear code (doesn't change) */ |
| code_int EOFCode; /* EOF code (ditto) */ |
| code_int free_code; /* LZW: first not-yet-used symbol code */ |
| code_int code_counter; /* not LZW: counts output symbols */ |
| |
| /* LZW hash table */ |
| code_int *hash_code; /* => hash table of symbol codes */ |
| hash_entry *hash_value; /* => hash table of symbol values */ |
| |
| /* GIF data packet construction buffer */ |
| int bytesinpkt; /* # of bytes in current packet */ |
| char packetbuf[256]; /* workspace for accumulating packet */ |
| |
| } gif_dest_struct; |
| |
| typedef gif_dest_struct *gif_dest_ptr; |
| |
| |
| /* |
| * Routines to package finished data bytes into GIF data blocks. |
| * A data block consists of a count byte (1..255) and that many data bytes. |
| */ |
| |
| LOCAL(void) |
| flush_packet(gif_dest_ptr dinfo) |
| /* flush any accumulated data */ |
| { |
| if (dinfo->bytesinpkt > 0) { /* never write zero-length packet */ |
| dinfo->packetbuf[0] = (char)dinfo->bytesinpkt++; |
| if (fwrite(dinfo->packetbuf, 1, dinfo->bytesinpkt, |
| dinfo->pub.output_file) != (size_t)dinfo->bytesinpkt) |
| ERREXIT(dinfo->cinfo, JERR_FILE_WRITE); |
| dinfo->bytesinpkt = 0; |
| } |
| } |
| |
| |
| /* Add a character to current packet; flush to disk if necessary */ |
| #define CHAR_OUT(dinfo, c) { \ |
| (dinfo)->packetbuf[++(dinfo)->bytesinpkt] = (char)(c); \ |
| if ((dinfo)->bytesinpkt >= 255) \ |
| flush_packet(dinfo); \ |
| } |
| |
| |
| /* Routine to convert variable-width codes into a byte stream */ |
| |
| LOCAL(void) |
| output(gif_dest_ptr dinfo, code_int code) |
| /* Emit a code of n_bits bits */ |
| /* Uses cur_accum and cur_bits to reblock into 8-bit bytes */ |
| { |
| dinfo->cur_accum |= ((long)code) << dinfo->cur_bits; |
| dinfo->cur_bits += dinfo->n_bits; |
| |
| while (dinfo->cur_bits >= 8) { |
| CHAR_OUT(dinfo, dinfo->cur_accum & 0xFF); |
| dinfo->cur_accum >>= 8; |
| dinfo->cur_bits -= 8; |
| } |
| |
| /* |
| * If the next entry is going to be too big for the code size, |
| * then increase it, if possible. We do this here to ensure |
| * that it's done in sync with the decoder's codesize increases. |
| */ |
| if (dinfo->free_code > dinfo->maxcode) { |
| dinfo->n_bits++; |
| if (dinfo->n_bits == MAX_LZW_BITS) |
| dinfo->maxcode = LZW_TABLE_SIZE; /* free_code will never exceed this */ |
| else |
| dinfo->maxcode = MAXCODE(dinfo->n_bits); |
| } |
| } |
| |
| |
| /* Compression initialization & termination */ |
| |
| |
| LOCAL(void) |
| clear_hash(gif_dest_ptr dinfo) |
| /* Fill the hash table with empty entries */ |
| { |
| /* It's sufficient to zero hash_code[] */ |
| memset(dinfo->hash_code, 0, HSIZE * sizeof(code_int)); |
| } |
| |
| |
| LOCAL(void) |
| clear_block(gif_dest_ptr dinfo) |
| /* Reset compressor and issue a Clear code */ |
| { |
| clear_hash(dinfo); /* delete all the symbols */ |
| dinfo->free_code = dinfo->ClearCode + 2; |
| output(dinfo, dinfo->ClearCode); /* inform decoder */ |
| dinfo->n_bits = dinfo->init_bits; /* reset code size */ |
| dinfo->maxcode = MAXCODE(dinfo->n_bits); |
| } |
| |
| |
| LOCAL(void) |
| compress_init(gif_dest_ptr dinfo, int i_bits) |
| /* Initialize compressor */ |
| { |
| /* init all the state variables */ |
| dinfo->n_bits = dinfo->init_bits = i_bits; |
| dinfo->maxcode = MAXCODE(dinfo->n_bits); |
| dinfo->ClearCode = ((code_int) 1 << (i_bits - 1)); |
| dinfo->EOFCode = dinfo->ClearCode + 1; |
| dinfo->code_counter = dinfo->free_code = dinfo->ClearCode + 2; |
| dinfo->first_byte = TRUE; /* no waiting symbol yet */ |
| /* init output buffering vars */ |
| dinfo->bytesinpkt = 0; |
| dinfo->cur_accum = 0; |
| dinfo->cur_bits = 0; |
| /* clear hash table */ |
| if (dinfo->hash_code != NULL) |
| clear_hash(dinfo); |
| /* GIF specifies an initial Clear code */ |
| output(dinfo, dinfo->ClearCode); |
| } |
| |
| |
| LOCAL(void) |
| compress_term(gif_dest_ptr dinfo) |
| /* Clean up at end */ |
| { |
| /* Flush out the buffered LZW code */ |
| if (!dinfo->first_byte) |
| output(dinfo, dinfo->waiting_code); |
| /* Send an EOF code */ |
| output(dinfo, dinfo->EOFCode); |
| /* Flush the bit-packing buffer */ |
| if (dinfo->cur_bits > 0) { |
| CHAR_OUT(dinfo, dinfo->cur_accum & 0xFF); |
| } |
| /* Flush the packet buffer */ |
| flush_packet(dinfo); |
| } |
| |
| |
| /* GIF header construction */ |
| |
| |
| LOCAL(void) |
| put_word(gif_dest_ptr dinfo, unsigned int w) |
| /* Emit a 16-bit word, LSB first */ |
| { |
| putc(w & 0xFF, dinfo->pub.output_file); |
| putc((w >> 8) & 0xFF, dinfo->pub.output_file); |
| } |
| |
| |
| LOCAL(void) |
| put_3bytes(gif_dest_ptr dinfo, int val) |
| /* Emit 3 copies of same byte value --- handy subr for colormap construction */ |
| { |
| putc(val, dinfo->pub.output_file); |
| putc(val, dinfo->pub.output_file); |
| putc(val, dinfo->pub.output_file); |
| } |
| |
| |
| LOCAL(void) |
| emit_header(gif_dest_ptr dinfo, int num_colors, JSAMPARRAY colormap) |
| /* Output the GIF file header, including color map */ |
| /* If colormap == NULL, synthesize a grayscale colormap */ |
| { |
| int BitsPerPixel, ColorMapSize, InitCodeSize, FlagByte; |
| int cshift = dinfo->cinfo->data_precision - 8; |
| int i; |
| |
| if (num_colors > 256) |
| ERREXIT1(dinfo->cinfo, JERR_TOO_MANY_COLORS, num_colors); |
| /* Compute bits/pixel and related values */ |
| BitsPerPixel = 1; |
| while (num_colors > (1 << BitsPerPixel)) |
| BitsPerPixel++; |
| ColorMapSize = 1 << BitsPerPixel; |
| if (BitsPerPixel <= 1) |
| InitCodeSize = 2; |
| else |
| InitCodeSize = BitsPerPixel; |
| /* |
| * Write the GIF header. |
| * Note that we generate a plain GIF87 header for maximum compatibility. |
| */ |
| putc('G', dinfo->pub.output_file); |
| putc('I', dinfo->pub.output_file); |
| putc('F', dinfo->pub.output_file); |
| putc('8', dinfo->pub.output_file); |
| putc('7', dinfo->pub.output_file); |
| putc('a', dinfo->pub.output_file); |
| /* Write the Logical Screen Descriptor */ |
| put_word(dinfo, (unsigned int)dinfo->cinfo->output_width); |
| put_word(dinfo, (unsigned int)dinfo->cinfo->output_height); |
| FlagByte = 0x80; /* Yes, there is a global color table */ |
| FlagByte |= (BitsPerPixel - 1) << 4; /* color resolution */ |
| FlagByte |= (BitsPerPixel - 1); /* size of global color table */ |
| putc(FlagByte, dinfo->pub.output_file); |
| putc(0, dinfo->pub.output_file); /* Background color index */ |
| putc(0, dinfo->pub.output_file); /* Reserved (aspect ratio in GIF89) */ |
| /* Write the Global Color Map */ |
| /* If the color map is more than 8 bits precision, */ |
| /* we reduce it to 8 bits by shifting */ |
| for (i = 0; i < ColorMapSize; i++) { |
| if (i < num_colors) { |
| if (colormap != NULL) { |
| if (dinfo->cinfo->out_color_space == JCS_RGB) { |
| /* Normal case: RGB color map */ |
| putc(colormap[0][i] >> cshift, dinfo->pub.output_file); |
| putc(colormap[1][i] >> cshift, dinfo->pub.output_file); |
| putc(colormap[2][i] >> cshift, dinfo->pub.output_file); |
| } else { |
| /* Grayscale "color map": possible if quantizing grayscale image */ |
| put_3bytes(dinfo, colormap[0][i] >> cshift); |
| } |
| } else { |
| /* Create a grayscale map of num_colors values, range 0..255 */ |
| put_3bytes(dinfo, (i * 255 + (num_colors - 1) / 2) / (num_colors - 1)); |
| } |
| } else { |
| /* fill out the map to a power of 2 */ |
| put_3bytes(dinfo, CENTERJSAMPLE >> cshift); |
| } |
| } |
| /* Write image separator and Image Descriptor */ |
| putc(',', dinfo->pub.output_file); /* separator */ |
| put_word(dinfo, 0); /* left/top offset */ |
| put_word(dinfo, 0); |
| put_word(dinfo, (unsigned int)dinfo->cinfo->output_width); /* image size */ |
| put_word(dinfo, (unsigned int)dinfo->cinfo->output_height); |
| /* flag byte: not interlaced, no local color map */ |
| putc(0x00, dinfo->pub.output_file); |
| /* Write Initial Code Size byte */ |
| putc(InitCodeSize, dinfo->pub.output_file); |
| |
| /* Initialize for compression of image data */ |
| compress_init(dinfo, InitCodeSize + 1); |
| } |
| |
| |
| /* |
| * Startup: write the file header. |
| */ |
| |
| METHODDEF(void) |
| start_output_gif(j_decompress_ptr cinfo, djpeg_dest_ptr dinfo) |
| { |
| gif_dest_ptr dest = (gif_dest_ptr)dinfo; |
| |
| if (cinfo->quantize_colors) |
| emit_header(dest, cinfo->actual_number_of_colors, cinfo->colormap); |
| else |
| emit_header(dest, 256, (JSAMPARRAY)NULL); |
| } |
| |
| |
| /* |
| * Write some pixel data. |
| * In this module rows_supplied will always be 1. |
| */ |
| |
| |
| /* |
| * The LZW algorithm proper |
| */ |
| |
| METHODDEF(void) |
| put_LZW_pixel_rows(j_decompress_ptr cinfo, djpeg_dest_ptr dinfo, |
| JDIMENSION rows_supplied) |
| { |
| gif_dest_ptr dest = (gif_dest_ptr)dinfo; |
| register JSAMPROW ptr; |
| register JDIMENSION col; |
| code_int c; |
| register hash_int i; |
| register hash_int disp; |
| register hash_entry probe_value; |
| |
| ptr = dest->pub.buffer[0]; |
| for (col = cinfo->output_width; col > 0; col--) { |
| /* Accept and compress one 8-bit byte */ |
| c = (code_int)(*ptr++); |
| |
| if (dest->first_byte) { /* need to initialize waiting_code */ |
| dest->waiting_code = c; |
| dest->first_byte = FALSE; |
| continue; |
| } |
| |
| /* Probe hash table to see if a symbol exists for |
| * waiting_code followed by c. |
| * If so, replace waiting_code by that symbol and continue. |
| */ |
| i = ((hash_int)c << (MAX_LZW_BITS - 8)) + dest->waiting_code; |
| /* i is less than twice 2**MAX_LZW_BITS, therefore less than twice HSIZE */ |
| if (i >= HSIZE) |
| i -= HSIZE; |
| |
| probe_value = HASH_ENTRY(dest->waiting_code, c); |
| |
| if (dest->hash_code[i] == 0) { |
| /* hit empty slot; desired symbol not in table */ |
| output(dest, dest->waiting_code); |
| if (dest->free_code < LZW_TABLE_SIZE) { |
| dest->hash_code[i] = dest->free_code++; /* add symbol to hashtable */ |
| dest->hash_value[i] = probe_value; |
| } else |
| clear_block(dest); |
| dest->waiting_code = c; |
| continue; |
| } |
| if (dest->hash_value[i] == probe_value) { |
| dest->waiting_code = dest->hash_code[i]; |
| continue; |
| } |
| |
| if (i == 0) /* secondary hash (after G. Knott) */ |
| disp = 1; |
| else |
| disp = HSIZE - i; |
| for (;;) { |
| i -= disp; |
| if (i < 0) |
| i += HSIZE; |
| if (dest->hash_code[i] == 0) { |
| /* hit empty slot; desired symbol not in table */ |
| output(dest, dest->waiting_code); |
| if (dest->free_code < LZW_TABLE_SIZE) { |
| dest->hash_code[i] = dest->free_code++; /* add symbol to hashtable */ |
| dest->hash_value[i] = probe_value; |
| } else |
| clear_block(dest); |
| dest->waiting_code = c; |
| break; |
| } |
| if (dest->hash_value[i] == probe_value) { |
| dest->waiting_code = dest->hash_code[i]; |
| break; |
| } |
| } |
| } |
| } |
| |
| |
| /* |
| * The pseudo-compression algorithm. |
| * |
| * In this version we simply output each pixel value as a separate symbol; |
| * thus, no compression occurs. In fact, there is expansion of one bit per |
| * pixel, because we use a symbol width one bit wider than the pixel width. |
| * |
| * GIF ordinarily uses variable-width symbols, and the decoder will expect |
| * to ratchet up the symbol width after a fixed number of symbols. |
| * To simplify the logic and keep the expansion penalty down, we emit a |
| * GIF Clear code to reset the decoder just before the width would ratchet up. |
| * Thus, all the symbols in the output file will have the same bit width. |
| * Note that emitting the Clear codes at the right times is a mere matter of |
| * counting output symbols and is in no way dependent on the LZW algorithm. |
| * |
| * With a small basic pixel width (low color count), Clear codes will be |
| * needed very frequently, causing the file to expand even more. So this |
| * simplistic approach wouldn't work too well on bilevel images, for example. |
| * But for output of JPEG conversions the pixel width will usually be 8 bits |
| * (129 to 256 colors), so the overhead added by Clear symbols is only about |
| * one symbol in every 256. |
| */ |
| |
| METHODDEF(void) |
| put_raw_pixel_rows(j_decompress_ptr cinfo, djpeg_dest_ptr dinfo, |
| JDIMENSION rows_supplied) |
| { |
| gif_dest_ptr dest = (gif_dest_ptr)dinfo; |
| register JSAMPROW ptr; |
| register JDIMENSION col; |
| code_int c; |
| |
| ptr = dest->pub.buffer[0]; |
| for (col = cinfo->output_width; col > 0; col--) { |
| c = (code_int)(*ptr++); |
| /* Accept and output one pixel value. |
| * The given value must be less than n_bits wide. |
| */ |
| |
| /* Output the given pixel value as a symbol. */ |
| output(dest, c); |
| /* Issue Clear codes often enough to keep the reader from ratcheting up |
| * its symbol size. |
| */ |
| if (dest->code_counter < dest->maxcode) { |
| dest->code_counter++; |
| } else { |
| output(dest, dest->ClearCode); |
| dest->code_counter = dest->ClearCode + 2; /* reset the counter */ |
| } |
| } |
| } |
| |
| |
| /* |
| * Finish up at the end of the file. |
| */ |
| |
| METHODDEF(void) |
| finish_output_gif(j_decompress_ptr cinfo, djpeg_dest_ptr dinfo) |
| { |
| gif_dest_ptr dest = (gif_dest_ptr)dinfo; |
| |
| /* Flush compression mechanism */ |
| compress_term(dest); |
| /* Write a zero-length data block to end the series */ |
| putc(0, dest->pub.output_file); |
| /* Write the GIF terminator mark */ |
| putc(';', dest->pub.output_file); |
| /* Make sure we wrote the output file OK */ |
| fflush(dest->pub.output_file); |
| if (ferror(dest->pub.output_file)) |
| ERREXIT(cinfo, JERR_FILE_WRITE); |
| } |
| |
| |
| /* |
| * Re-calculate buffer dimensions based on output dimensions. |
| */ |
| |
| METHODDEF(void) |
| calc_buffer_dimensions_gif(j_decompress_ptr cinfo, djpeg_dest_ptr dinfo) |
| { |
| } |
| |
| |
| /* |
| * The module selection routine for GIF format output. |
| */ |
| |
| GLOBAL(djpeg_dest_ptr) |
| jinit_write_gif(j_decompress_ptr cinfo, boolean is_lzw) |
| { |
| gif_dest_ptr dest; |
| |
| /* Create module interface object, fill in method pointers */ |
| dest = (gif_dest_ptr) |
| (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE, |
| sizeof(gif_dest_struct)); |
| dest->cinfo = cinfo; /* make back link for subroutines */ |
| dest->pub.start_output = start_output_gif; |
| dest->pub.finish_output = finish_output_gif; |
| dest->pub.calc_buffer_dimensions = calc_buffer_dimensions_gif; |
| |
| if (cinfo->out_color_space != JCS_GRAYSCALE && |
| cinfo->out_color_space != JCS_RGB) |
| ERREXIT(cinfo, JERR_GIF_COLORSPACE); |
| |
| /* Force quantization if color or if > 8 bits input */ |
| if (cinfo->out_color_space != JCS_GRAYSCALE || cinfo->data_precision > 8) { |
| /* Force quantization to at most 256 colors */ |
| cinfo->quantize_colors = TRUE; |
| if (cinfo->desired_number_of_colors > 256) |
| cinfo->desired_number_of_colors = 256; |
| } |
| |
| /* Calculate output image dimensions so we can allocate space */ |
| jpeg_calc_output_dimensions(cinfo); |
| |
| if (cinfo->output_components != 1) /* safety check: just one component? */ |
| ERREXIT(cinfo, JERR_GIF_BUG); |
| |
| /* Create decompressor output buffer. */ |
| dest->pub.buffer = (*cinfo->mem->alloc_sarray) |
| ((j_common_ptr)cinfo, JPOOL_IMAGE, cinfo->output_width, (JDIMENSION)1); |
| dest->pub.buffer_height = 1; |
| |
| if (is_lzw) { |
| dest->pub.put_pixel_rows = put_LZW_pixel_rows; |
| /* Allocate space for hash table */ |
| dest->hash_code = (code_int *) |
| (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE, |
| HSIZE * sizeof(code_int)); |
| dest->hash_value = (hash_entry *) |
| (*cinfo->mem->alloc_large) ((j_common_ptr)cinfo, JPOOL_IMAGE, |
| HSIZE * sizeof(hash_entry)); |
| } else { |
| dest->pub.put_pixel_rows = put_raw_pixel_rows; |
| /* Mark tables unused */ |
| dest->hash_code = NULL; |
| dest->hash_value = NULL; |
| } |
| |
| return (djpeg_dest_ptr)dest; |
| } |
| |
| #endif /* GIF_SUPPORTED */ |