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DEFINITIONS
This source file includes following definitions.
- gdImageGifPtr
- gdImageGif
- gdImageGifCtx
- colorstobpp
- BumpPixel
- GIFNextPixel
- GIFEncode
- compress
- output
- cl_block
- cl_hash
- char_init
- char_out
- flush_char
- gifPutWord
#include <stdio.h>
#include <math.h>
#include <string.h>
#include <stdlib.h>
#include "gd.h"
/* Code drawn from ppmtogif.c, from the pbmplus package
**
** Based on GIFENCOD by David Rowley <mgardi@watdscu.waterloo.edu>. A
** Lempel-Zim compression based on "compress".
**
** Modified by Marcel Wijkstra <wijkstra@fwi.uva.nl>
**
** 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.
**
** The Graphics Interchange Format(c) is the Copyright property of
** CompuServe Incorporated. GIF(sm) is a Service Mark property of
** CompuServe Incorporated.
*/
/*
* a code_int must be able to hold 2**GIFBITS values of type int, and also -1
*/
typedef int code_int;
#ifdef SIGNED_COMPARE_SLOW
typedef unsigned long int count_int;
typedef unsigned short int count_short;
#else /*SIGNED_COMPARE_SLOW*/
typedef long int count_int;
#endif /*SIGNED_COMPARE_SLOW*/
/* 2.0.28: threadsafe */
#define maxbits GIFBITS
/* should NEVER generate this code */
#define maxmaxcode ((code_int)1 << GIFBITS)
#define HSIZE 5003 /* 80% occupancy */
#define hsize HSIZE /* Apparently invariant, left over from
compress */
typedef struct {
int Width, Height;
int curx, cury;
long CountDown;
int Pass;
int Interlace;
int n_bits; /* number of bits/code */
code_int maxcode; /* maximum code, given n_bits */
count_int htab [HSIZE];
unsigned short codetab [HSIZE];
code_int free_ent; /* first unused entry */
/*
* block compression parameters -- after all codes are used up,
* and compression rate changes, start over.
*/
int clear_flg;
int offset;
long int in_count; /* length of input */
long int out_count; /* # of codes output (for debugging) */
int g_init_bits;
gdIOCtx * g_outfile;
int ClearCode;
int EOFCode;
unsigned long cur_accum;
int cur_bits;
/*
* Number of characters so far in this 'packet'
*/
int a_count;
/*
* Define the storage for the packet accumulator
*/
char accum[ 256 ];
} GifCtx;
static int gifPutWord(int w, gdIOCtx *out);
static int colorstobpp(int colors);
static void BumpPixel (GifCtx *ctx);
static int GIFNextPixel (gdImagePtr im, GifCtx *ctx);
static void GIFEncode (gdIOCtxPtr fp, int GWidth, int GHeight, int GInterlace, int Background, int Transparent, int BitsPerPixel, int *Red, int *Green, int *Blue, gdImagePtr im);
static void compress (int init_bits, gdIOCtx *outfile, gdImagePtr im, GifCtx *ctx);
static void output (code_int code, GifCtx *ctx);
static void cl_block (GifCtx *ctx);
static void cl_hash (register count_int chsize, GifCtx *ctx);
static void char_init (GifCtx *ctx);
static void char_out (int c, GifCtx *ctx);
static void flush_char (GifCtx *ctx);
void * gdImageGifPtr (gdImagePtr im, int *size)
{
void *rv;
gdIOCtx *out = gdNewDynamicCtx (2048, NULL);
gdImageGifCtx (im, out);
rv = gdDPExtractData (out, size);
out->gd_free (out);
return rv;
}
void gdImageGif (gdImagePtr im, FILE * outFile)
{
gdIOCtx *out = gdNewFileCtx (outFile);
gdImageGifCtx (im, out);
out->gd_free (out);
}
void gdImageGifCtx(gdImagePtr im, gdIOCtxPtr out)
{
gdImagePtr pim = 0, tim = im;
int interlace, transparent, BitsPerPixel;
interlace = im->interlace;
transparent = im->transparent;
if (im->trueColor) {
/* Expensive, but the only way that produces an
acceptable result: mix down to a palette
based temporary image. */
pim = gdImageCreatePaletteFromTrueColor(im, 1, 256);
if (!pim) {
return;
}
tim = pim;
}
BitsPerPixel = colorstobpp(tim->colorsTotal);
/* All set, let's do it. */
GIFEncode(
out, tim->sx, tim->sy, tim->interlace, 0, tim->transparent, BitsPerPixel,
tim->red, tim->green, tim->blue, tim);
if (pim) {
/* Destroy palette based temporary image. */
gdImageDestroy( pim);
}
}
static int
colorstobpp(int colors)
{
int bpp = 0;
if ( colors <= 2 )
bpp = 1;
else if ( colors <= 4 )
bpp = 2;
else if ( colors <= 8 )
bpp = 3;
else if ( colors <= 16 )
bpp = 4;
else if ( colors <= 32 )
bpp = 5;
else if ( colors <= 64 )
bpp = 6;
else if ( colors <= 128 )
bpp = 7;
else if ( colors <= 256 )
bpp = 8;
return bpp;
}
/*****************************************************************************
*
* GIFENCODE.C - GIF Image compression interface
*
* GIFEncode( FName, GHeight, GWidth, GInterlace, Background, Transparent,
* BitsPerPixel, Red, Green, Blue, gdImagePtr )
*
*****************************************************************************/
#define TRUE 1
#define FALSE 0
/*
* Bump the 'curx' and 'cury' to point to the next pixel
*/
static void
BumpPixel(GifCtx *ctx)
{
/*
* Bump the current X position
*/
++(ctx->curx);
/*
* If we are at the end of a scan line, set curx back to the beginning
* If we are interlaced, bump the cury to the appropriate spot,
* otherwise, just increment it.
*/
if( ctx->curx == ctx->Width ) {
ctx->curx = 0;
if( !ctx->Interlace )
++(ctx->cury);
else {
switch( ctx->Pass ) {
case 0:
ctx->cury += 8;
if( ctx->cury >= ctx->Height ) {
++(ctx->Pass);
ctx->cury = 4;
}
break;
case 1:
ctx->cury += 8;
if( ctx->cury >= ctx->Height ) {
++(ctx->Pass);
ctx->cury = 2;
}
break;
case 2:
ctx->cury += 4;
if( ctx->cury >= ctx->Height ) {
++(ctx->Pass);
ctx->cury = 1;
}
break;
case 3:
ctx->cury += 2;
break;
}
}
}
}
/*
* Return the next pixel from the image
*/
static int
GIFNextPixel(gdImagePtr im, GifCtx *ctx)
{
int r;
if( ctx->CountDown == 0 )
return EOF;
--(ctx->CountDown);
r = gdImageGetPixel(im, ctx->curx, ctx->cury);
BumpPixel(ctx);
return r;
}
/* public */
static void
GIFEncode(gdIOCtxPtr fp, int GWidth, int GHeight, int GInterlace, int Background, int Transparent, int BitsPerPixel, int *Red, int *Green, int *Blue, gdImagePtr im)
{
int B;
int RWidth, RHeight;
int LeftOfs, TopOfs;
int Resolution;
int ColorMapSize;
int InitCodeSize;
int i;
GifCtx ctx;
memset(&ctx, 0, sizeof(ctx));
ctx.Interlace = GInterlace;
ctx.in_count = 1;
ColorMapSize = 1 << BitsPerPixel;
RWidth = ctx.Width = GWidth;
RHeight = ctx.Height = GHeight;
LeftOfs = TopOfs = 0;
Resolution = BitsPerPixel;
/*
* Calculate number of bits we are expecting
*/
ctx.CountDown = (long)ctx.Width * (long)ctx.Height;
/*
* Indicate which pass we are on (if interlace)
*/
ctx.Pass = 0;
/*
* The initial code size
*/
if( BitsPerPixel <= 1 )
InitCodeSize = 2;
else
InitCodeSize = BitsPerPixel;
/*
* Set up the current x and y position
*/
ctx.curx = ctx.cury = 0;
/*
* Write the Magic header
*/
gdPutBuf(Transparent < 0 ? "GIF87a" : "GIF89a", 6, fp );
/*
* Write out the screen width and height
*/
gifPutWord( RWidth, fp );
gifPutWord( RHeight, fp );
/*
* Indicate that there is a global colour map
*/
B = 0x80; /* Yes, there is a color map */
/*
* OR in the resolution
*/
B |= (Resolution - 1) << 5;
/*
* OR in the Bits per Pixel
*/
B |= (BitsPerPixel - 1);
/*
* Write it out
*/
gdPutC( B, fp );
/*
* Write out the Background colour
*/
gdPutC( Background, fp );
/*
* Byte of 0's (future expansion)
*/
gdPutC( 0, fp );
/*
* Write out the Global Colour Map
*/
for( i=0; i<ColorMapSize; ++i ) {
gdPutC( Red[i], fp );
gdPutC( Green[i], fp );
gdPutC( Blue[i], fp );
}
/*
* Write out extension for transparent colour index, if necessary.
*/
if ( Transparent >= 0 ) {
gdPutC( '!', fp );
gdPutC( 0xf9, fp );
gdPutC( 4, fp );
gdPutC( 1, fp );
gdPutC( 0, fp );
gdPutC( 0, fp );
gdPutC( (unsigned char) Transparent, fp );
gdPutC( 0, fp );
}
/*
* Write an Image separator
*/
gdPutC( ',', fp );
/*
* Write the Image header
*/
gifPutWord( LeftOfs, fp );
gifPutWord( TopOfs, fp );
gifPutWord( ctx.Width, fp );
gifPutWord( ctx.Height, fp );
/*
* Write out whether or not the image is interlaced
*/
if( ctx.Interlace )
gdPutC( 0x40, fp );
else
gdPutC( 0x00, fp );
/*
* Write out the initial code size
*/
gdPutC( InitCodeSize, fp );
/*
* Go and actually compress the data
*/
compress( InitCodeSize+1, fp, im, &ctx );
/*
* Write out a Zero-length packet (to end the series)
*/
gdPutC( 0, fp );
/*
* Write the GIF file terminator
*/
gdPutC( ';', fp );
}
/***************************************************************************
*
* GIFCOMPR.C - GIF Image compression routines
*
* Lempel-Ziv compression based on 'compress'. GIF modifications by
* David Rowley (mgardi@watdcsu.waterloo.edu)
*
***************************************************************************/
/*
* General DEFINEs
*/
#define GIFBITS 12
#ifdef NO_UCHAR
typedef char char_type;
#else /*NO_UCHAR*/
typedef unsigned char char_type;
#endif /*NO_UCHAR*/
/*
*
* GIF Image compression - modified 'compress'
*
* Based on: compress.c - File compression ala IEEE Computer, June 1984.
*
* By Authors: Spencer W. Thomas (decvax!harpo!utah-cs!utah-gr!thomas)
* Jim McKie (decvax!mcvax!jim)
* Steve Davies (decvax!vax135!petsd!peora!srd)
* Ken Turkowski (decvax!decwrl!turtlevax!ken)
* James A. Woods (decvax!ihnp4!ames!jaw)
* Joe Orost (decvax!vax135!petsd!joe)
*
*/
#include <ctype.h>
#define ARGVAL() (*++(*argv) || (--argc && *++argv))
#ifdef COMPATIBLE /* But wrong! */
# define MAXCODE(n_bits) ((code_int) 1 << (n_bits) - 1)
#else /*COMPATIBLE*/
# define MAXCODE(n_bits) (((code_int) 1 << (n_bits)) - 1)
#endif /*COMPATIBLE*/
#define HashTabOf(i) ctx->htab[i]
#define CodeTabOf(i) ctx->codetab[i]
/*
* To save much memory, we overlay the table used by compress() with those
* used by decompress(). The tab_prefix table is the same size and type
* as the codetab. The tab_suffix table needs 2**GIFBITS characters. We
* get this from the beginning of htab. The output stack uses the rest
* of htab, and contains characters. There is plenty of room for any
* possible stack (stack used to be 8000 characters).
*/
#define tab_prefixof(i) CodeTabOf(i)
#define tab_suffixof(i) ((char_type*)(htab))[i]
#define de_stack ((char_type*)&tab_suffixof((code_int)1<<GIFBITS))
/*
* compress stdin to stdout
*
* Algorithm: use open addressing double hashing (no chaining) on the
* prefix code / next 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. Here, the modular division first probe is gives way
* to a faster exclusive-or manipulation. Also do block compression with
* an adaptive reset, whereby the code table is cleared when the compression
* ratio decreases, but after the table fills. The variable-length output
* codes are re-sized at this point, and a special CLEAR code is generated
* for the decompressor. Late addition: construct the table according to
* file size for noticeable speed improvement on small files. Please direct
* questions about this implementation to ames!jaw.
*/
static void
output(code_int code, GifCtx *ctx);
static void
compress(int init_bits, gdIOCtxPtr outfile, gdImagePtr im, GifCtx *ctx)
{
register long fcode;
register code_int i /* = 0 */;
register int c;
register code_int ent;
register code_int disp;
register code_int hsize_reg;
register int hshift;
/*
* Set up the globals: g_init_bits - initial number of bits
* g_outfile - pointer to output file
*/
ctx->g_init_bits = init_bits;
ctx->g_outfile = outfile;
/*
* Set up the necessary values
*/
ctx->offset = 0;
ctx->out_count = 0;
ctx->clear_flg = 0;
ctx->in_count = 1;
ctx->maxcode = MAXCODE(ctx->n_bits = ctx->g_init_bits);
ctx->ClearCode = (1 << (init_bits - 1));
ctx->EOFCode = ctx->ClearCode + 1;
ctx->free_ent = ctx->ClearCode + 2;
char_init(ctx);
ent = GIFNextPixel( im, ctx );
hshift = 0;
for ( fcode = (long) hsize; fcode < 65536L; fcode *= 2L )
++hshift;
hshift = 8 - hshift; /* set hash code range bound */
hsize_reg = hsize;
cl_hash( (count_int) hsize_reg, ctx ); /* clear hash table */
output( (code_int)ctx->ClearCode, ctx );
#ifdef SIGNED_COMPARE_SLOW
while ( (c = GIFNextPixel( im )) != (unsigned) EOF ) {
#else /*SIGNED_COMPARE_SLOW*/
while ( (c = GIFNextPixel( im, ctx )) != EOF ) { /* } */
#endif /*SIGNED_COMPARE_SLOW*/
++(ctx->in_count);
fcode = (long) (((long) c << maxbits) + ent);
i = (((code_int)c << hshift) ^ ent); /* xor hashing */
if ( HashTabOf (i) == fcode ) {
ent = CodeTabOf (i);
continue;
} else if ( (long)HashTabOf (i) < 0 ) /* empty slot */
goto nomatch;
disp = hsize_reg - i; /* secondary hash (after G. Knott) */
if ( i == 0 )
disp = 1;
probe:
if ( (i -= disp) < 0 )
i += hsize_reg;
if ( HashTabOf (i) == fcode ) {
ent = CodeTabOf (i);
continue;
}
if ( (long)HashTabOf (i) > 0 )
goto probe;
nomatch:
output ( (code_int) ent, ctx );
++(ctx->out_count);
ent = c;
#ifdef SIGNED_COMPARE_SLOW
if ( (unsigned) ctx->free_ent < (unsigned) maxmaxcode) {
#else /*SIGNED_COMPARE_SLOW*/
if ( ctx->free_ent < maxmaxcode ) { /* } */
#endif /*SIGNED_COMPARE_SLOW*/
CodeTabOf (i) = ctx->free_ent++; /* code -> hashtable */
HashTabOf (i) = fcode;
} else
cl_block(ctx);
}
/*
* Put out the final code.
*/
output( (code_int)ent, ctx );
++(ctx->out_count);
output( (code_int) ctx->EOFCode, ctx );
}
/*****************************************************************
* TAG( output )
*
* Output the given code.
* Inputs:
* code: A n_bits-bit integer. If == -1, then EOF. This assumes
* that n_bits =< (long)wordsize - 1.
* Outputs:
* Outputs code to the file.
* Assumptions:
* Chars are 8 bits long.
* Algorithm:
* Maintain a GIFBITS character long buffer (so that 8 codes will
* fit in it exactly). Use the VAX insv instruction to insert each
* code in turn. When the buffer fills up empty it and start over.
*/
static unsigned long masks[] = { 0x0000, 0x0001, 0x0003, 0x0007, 0x000F,
0x001F, 0x003F, 0x007F, 0x00FF,
0x01FF, 0x03FF, 0x07FF, 0x0FFF,
0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF };
static void
output(code_int code, GifCtx *ctx)
{
ctx->cur_accum &= masks[ ctx->cur_bits ];
if( ctx->cur_bits > 0 )
ctx->cur_accum |= ((long)code << ctx->cur_bits);
else
ctx->cur_accum = code;
ctx->cur_bits += ctx->n_bits;
while( ctx->cur_bits >= 8 ) {
char_out( (unsigned int)(ctx->cur_accum & 0xff), ctx );
ctx->cur_accum >>= 8;
ctx->cur_bits -= 8;
}
/*
* If the next entry is going to be too big for the code size,
* then increase it, if possible.
*/
if ( ctx->free_ent > ctx->maxcode || ctx->clear_flg ) {
if( ctx->clear_flg ) {
ctx->maxcode = MAXCODE (ctx->n_bits = ctx->g_init_bits);
ctx->clear_flg = 0;
} else {
++(ctx->n_bits);
if ( ctx->n_bits == maxbits )
ctx->maxcode = maxmaxcode;
else
ctx->maxcode = MAXCODE(ctx->n_bits);
}
}
if( code == ctx->EOFCode ) {
/*
* At EOF, write the rest of the buffer.
*/
while( ctx->cur_bits > 0 ) {
char_out( (unsigned int)(ctx->cur_accum & 0xff), ctx);
ctx->cur_accum >>= 8;
ctx->cur_bits -= 8;
}
flush_char(ctx);
}
}
/*
* Clear out the hash table
*/
static void
cl_block (GifCtx *ctx) /* table clear for block compress */
{
cl_hash ( (count_int) hsize, ctx );
ctx->free_ent = ctx->ClearCode + 2;
ctx->clear_flg = 1;
output( (code_int)ctx->ClearCode, ctx);
}
static void
cl_hash(register count_int chsize, GifCtx *ctx) /* reset code table */
{
register count_int *htab_p = ctx->htab+chsize;
register long i;
register long m1 = -1;
i = chsize - 16;
do { /* might use Sys V memset(3) here */
*(htab_p-16) = m1;
*(htab_p-15) = m1;
*(htab_p-14) = m1;
*(htab_p-13) = m1;
*(htab_p-12) = m1;
*(htab_p-11) = m1;
*(htab_p-10) = m1;
*(htab_p-9) = m1;
*(htab_p-8) = m1;
*(htab_p-7) = m1;
*(htab_p-6) = m1;
*(htab_p-5) = m1;
*(htab_p-4) = m1;
*(htab_p-3) = m1;
*(htab_p-2) = m1;
*(htab_p-1) = m1;
htab_p -= 16;
} while ((i -= 16) >= 0);
for ( i += 16; i > 0; --i )
*--htab_p = m1;
}
/******************************************************************************
*
* GIF Specific routines
*
******************************************************************************/
/*
* Set up the 'byte output' routine
*/
static void
char_init(GifCtx *ctx)
{
ctx->a_count = 0;
}
/*
* Add a character to the end of the current packet, and if it is 254
* characters, flush the packet to disk.
*/
static void
char_out(int c, GifCtx *ctx)
{
ctx->accum[ ctx->a_count++ ] = c;
if( ctx->a_count >= 254 )
flush_char(ctx);
}
/*
* Flush the packet to disk, and reset the accumulator
*/
static void
flush_char(GifCtx *ctx)
{
if( ctx->a_count > 0 ) {
gdPutC( ctx->a_count, ctx->g_outfile );
gdPutBuf( ctx->accum, ctx->a_count, ctx->g_outfile );
ctx->a_count = 0;
}
}
static int gifPutWord(int w, gdIOCtx *out)
{
/* Byte order is little-endian */
gdPutC(w & 0xFF, out);
gdPutC((w >> 8) & 0xFF, out);
return 0;
}