+++ /dev/null
-/*
- * wrgif.c
- *
- * Copyright (C) 1991-1997, Thomas G. Lane.
- * This file is part of the Independent JPEG Group's software.
- * For conditions of distribution and use, see the accompanying README file.
- *
- * This file contains routines to write output images in GIF format.
- *
- **************************************************************************
- * NOTE: to avoid entanglements with Unisys' patent on LZW compression, *
- * this code has been modified to output "uncompressed GIF" files. *
- * There is no trace of the LZW algorithm in this file. *
- **************************************************************************
- *
- * 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.
- *
- * We are also required to state that
- * "The Graphics Interchange Format(c) is the Copyright property of
- * CompuServe Incorporated. GIF(sm) is a Service Mark property of
- * CompuServe Incorporated."
- */
-
-#include "cdjpeg.h" /* Common decls for cjpeg/djpeg applications */
-
-#ifdef GIF_SUPPORTED
-
-
-/* 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 */
- int maxcode; /* maximum code, given n_bits */
- INT32 cur_accum; /* holds bits not yet output */
- int cur_bits; /* # of bits in cur_accum */
-
- /* State for GIF code assignment */
- int ClearCode; /* clear code (doesn't change) */
- int EOFCode; /* EOF code (ditto) */
- int code_counter; /* counts output symbols */
-
- /* 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;
-
-/* Largest value that will fit in N bits */
-#define MAXCODE(n_bits) ((1 << (n_bits)) - 1)
-
-
-/*
- * 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 (JFWRITE(dinfo->pub.output_file, dinfo->packetbuf, dinfo->bytesinpkt)
- != (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, int code)
-/* Emit a code of n_bits bits */
-/* Uses cur_accum and cur_bits to reblock into 8-bit bytes */
-{
- dinfo->cur_accum |= ((INT32) 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;
- }
-}
-
-
-/* The pseudo-compression algorithm.
- *
- * In this module 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 patent.
- *
- * 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.
- */
-
-LOCAL(void)
-compress_init (gif_dest_ptr dinfo, int i_bits)
-/* Initialize pseudo-compressor */
-{
- /* init all the state variables */
- dinfo->n_bits = i_bits;
- dinfo->maxcode = MAXCODE(dinfo->n_bits);
- dinfo->ClearCode = (1 << (i_bits - 1));
- dinfo->EOFCode = dinfo->ClearCode + 1;
- dinfo->code_counter = dinfo->ClearCode + 2;
- /* init output buffering vars */
- dinfo->bytesinpkt = 0;
- dinfo->cur_accum = 0;
- dinfo->cur_bits = 0;
- /* GIF specifies an initial Clear code */
- output(dinfo, dinfo->ClearCode);
-}
-
-
-LOCAL(void)
-compress_pixel (gif_dest_ptr dinfo, int c)
-/* Accept and "compress" one pixel value.
- * The given value must be less than n_bits wide.
- */
-{
- /* Output the given pixel value as a symbol. */
- output(dinfo, c);
- /* Issue Clear codes often enough to keep the reader from ratcheting up
- * its symbol size.
- */
- if (dinfo->code_counter < dinfo->maxcode) {
- dinfo->code_counter++;
- } else {
- output(dinfo, dinfo->ClearCode);
- dinfo->code_counter = dinfo->ClearCode + 2; /* reset the counter */
- }
-}
-
-
-LOCAL(void)
-compress_term (gif_dest_ptr dinfo)
-/* Clean up at end */
-{
- /* 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 gray-scale 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(GETJSAMPLE(colormap[0][i]) >> cshift, dinfo->pub.output_file);
- putc(GETJSAMPLE(colormap[1][i]) >> cshift, dinfo->pub.output_file);
- putc(GETJSAMPLE(colormap[2][i]) >> cshift, dinfo->pub.output_file);
- } else {
- /* Grayscale "color map": possible if quantizing grayscale image */
- put_3bytes(dinfo, GETJSAMPLE(colormap[0][i]) >> cshift);
- }
- } else {
- /* Create a gray-scale 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, 0);
- }
- }
- /* 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.
- */
-
-METHODDEF(void)
-put_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;
-
- ptr = dest->pub.buffer[0];
- for (col = cinfo->output_width; col > 0; col--) {
- compress_pixel(dest, GETJSAMPLE(*ptr++));
- }
-}
-
-
-/*
- * 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);
-}
-
-
-/*
- * The module selection routine for GIF format output.
- */
-
-GLOBAL(djpeg_dest_ptr)
-jinit_write_gif (j_decompress_ptr cinfo)
-{
- 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.put_pixel_rows = put_pixel_rows;
- dest->pub.finish_output = finish_output_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;
-
- return (djpeg_dest_ptr) dest;
-}
-
-#endif /* GIF_SUPPORTED */
projects / synfig.git / blobdiff