400 lines
13 KiB
C
Executable File
400 lines
13 KiB
C
Executable File
/*
|
|
* 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 */
|