This is wrgif.c in view mode; [Download] [Up]
/*
* wrgif.c
*
* Copyright (C) 1991-1996, 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.
*
**************************************************************************
* WARNING: You will need an LZW patent license from Unisys in order to *
* use this file legally in any commercial or shareware application. *
**************************************************************************
*
* 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.
*
* 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
#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.
*
* The hash_value[] table is allocated from FAR heap space since it would
* use up rather a lot of the near data space in a PC.
*/
typedef INT32 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 */
INT32 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 LZW code assignment */
code_int ClearCode; /* clear code (doesn't change) */
code_int EOFCode; /* EOF code (ditto) */
code_int free_code; /* first not-yet-used symbol code */
/* LZW hash table */
code_int *hash_code; /* => hash table of symbol codes */
hash_entry FAR *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 compressed 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, 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 |= ((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;
}
/*
* 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);
}
}
/* The LZW algorithm proper */
LOCAL(void)
clear_hash (gif_dest_ptr dinfo)
/* Fill the hash table with empty entries */
{
/* It's sufficient to zero hash_code[] */
MEMZERO(dinfo->hash_code, 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 LZW 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->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 */
clear_hash(dinfo);
/* GIF specifies an initial Clear code */
output(dinfo, dinfo->ClearCode);
}
LOCAL(void)
compress_byte (gif_dest_ptr dinfo, int c)
/* Accept and compress one 8-bit byte */
{
register hash_int i;
register hash_int disp;
register hash_entry probe_value;
if (dinfo->first_byte) { /* need to initialize waiting_code */
dinfo->waiting_code = c;
dinfo->first_byte = FALSE;
return;
}
/* Probe hash table to see if a symbol exists for
* waiting_code followed by c.
* If so, replace waiting_code by that symbol and return.
*/
i = ((hash_int) c << (MAX_LZW_BITS-8)) + dinfo->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(dinfo->waiting_code, c);
if (dinfo->hash_code[i] != 0) { /* is first probed slot empty? */
if (dinfo->hash_value[i] == probe_value) {
dinfo->waiting_code = dinfo->hash_code[i];
return;
}
if (i == 0) /* secondary hash (after G. Knott) */
disp = 1;
else
disp = HSIZE - i;
for (;;) {
i -= disp;
if (i < 0)
i += HSIZE;
if (dinfo->hash_code[i] == 0)
break; /* hit empty slot */
if (dinfo->hash_value[i] == probe_value) {
dinfo->waiting_code = dinfo->hash_code[i];
return;
}
}
}
/* here when hashtable[i] is an empty slot; desired symbol not in table */
output(dinfo, dinfo->waiting_code);
if (dinfo->free_code < LZW_TABLE_SIZE) {
dinfo->hash_code[i] = dinfo->free_code++; /* add symbol to hashtable */
dinfo->hash_value[i] = probe_value;
} else
clear_block(dinfo);
dinfo->waiting_code = c;
}
LOCAL(void)
compress_term (gif_dest_ptr dinfo)
/* Clean up at end */
{
/* Flush out the buffered 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 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 LZW 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_byte(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 LZW 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;
/* 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 FAR *)
(*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
HSIZE * SIZEOF(hash_entry));
return (djpeg_dest_ptr) dest;
}
#endif /* GIF_SUPPORTED */
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.