gd_gif_out.c

Linux/Unix下的绘图函数库（Graphic Drawing Library）

#include <stdio.h>
#include <math.h>
#include <string.h>
#include <stdlib.h>
#include "gd.h"
#include "gdhelpers.h"

/* Code drawn from ppmtogif.c, from the pbmplus package
**
** Based on GIFENCOD by David Rowley <[e-mail]>. A
** Lempel-Zim compression based on "compress".
**
** Modified by Marcel Wijkstra <[e-mail]>
**
** 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 GIFAnimEncode (gdIOCtxPtr fp, int IWidth, int IHeight, int LeftOfs, int TopOfs, int GInterlace, int Transparent, int Delay, int Disposal, 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);
BGD_DECLARE(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;
}

BGD_DECLARE(void) gdImageGif (gdImagePtr im, FILE * outFile)
{
  gdIOCtx *out = gdNewFileCtx (outFile);
  gdImageGifCtx (im, out);
  out->gd_free (out);
}

BGD_DECLARE(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, interlace, 0, transparent, BitsPerPixel,
		tim->red, tim->green, tim->blue, tim);
	if (pim) {
		/* Destroy palette based temporary image. */
		gdImageDestroy(	pim);
	}
}

BGD_DECLARE(void *) gdImageGifAnimBeginPtr (gdImagePtr im, int *size, int GlobalCM, int Loops)
{
  void *rv;
  gdIOCtx *out = gdNewDynamicCtx (2048, NULL);
  gdImageGifAnimBeginCtx(im, out, GlobalCM, Loops);
  rv = gdDPExtractData (out, size);
  out->gd_free (out);
  return rv;
}

BGD_DECLARE(void) gdImageGifAnimBegin (gdImagePtr im, FILE *outFile, int GlobalCM, int Loops)
{
  gdIOCtx *out = gdNewFileCtx (outFile);
  gdImageGifAnimBeginCtx (im, out, GlobalCM, Loops);
  out->gd_free (out);
}

BGD_DECLARE(void) gdImageGifAnimBeginCtx(gdImagePtr im, gdIOCtxPtr out, int GlobalCM, int Loops)
{
	int B;
	int RWidth, RHeight;
	int Resolution;
	int ColorMapSize;
	int BitsPerPixel;
	int Background = 0;
	int i;

	/* Default is to use global color map */
	if (GlobalCM < 0) GlobalCM = 1;

	BitsPerPixel = colorstobpp(im->colorsTotal);
        ColorMapSize = 1 << BitsPerPixel;

        RWidth = im->sx;
        RHeight = im->sy;

        Resolution = BitsPerPixel;

        /*
         * Write the Magic header
         */
        gdPutBuf("GIF89a", 6, out );

        /*
         * Write out the screen width and height
         */
        gifPutWord( RWidth, out );
        gifPutWord( RHeight, out );

        /*
         * Indicate that there is a global colour map
         */
        B = GlobalCM ? 0x80 : 0;

        /*
         * OR in the resolution
         */
        B |= (Resolution - 1) << 5;

        /*
         * OR in the Bits per Pixel
         */
        B |= (BitsPerPixel - 1);

        /*
         * Write it out
         */
        gdPutC( B, out );

        /*
         * Write out the Background colour
         */
        gdPutC( Background, out );

        /*
         * Byte of 0's (future expansion)
         */
        gdPutC( 0, out );

        /*
         * Write out the Global Colour Map
         */
	if (GlobalCM)
		for( i=0; i<ColorMapSize; ++i ) {
			gdPutC( im->red[i], out );
			gdPutC( im->green[i], out );
			gdPutC( im->blue[i], out );
		}

	if (Loops >= 0) {
		gdPutBuf( "!\377\13NETSCAPE2.0\3\1", 16, out );
		gifPutWord( Loops, out );
		gdPutC( 0, out );
	}
}

BGD_DECLARE(void *) gdImageGifAnimAddPtr (gdImagePtr im, int *size, int LocalCM, int LeftOfs, int TopOfs, int Delay, int Disposal, gdImagePtr previm)
{
  void *rv;
  gdIOCtx *out = gdNewDynamicCtx (2048, NULL);
  gdImageGifAnimAddCtx(im, out, LocalCM, LeftOfs, TopOfs, Delay, Disposal, previm);
  rv = gdDPExtractData (out, size);
  out->gd_free (out);
  return rv;
}

BGD_DECLARE(void) gdImageGifAnimAdd (gdImagePtr im, FILE * outFile, int LocalCM, int LeftOfs, int TopOfs, int Delay, int Disposal, gdImagePtr previm)
{
  gdIOCtx *out = gdNewFileCtx (outFile);
  gdImageGifAnimAddCtx (im, out, LocalCM, LeftOfs, TopOfs, Delay, Disposal, previm);
  out->gd_free (out);
}

static int
comparewithmap (gdImagePtr im1, gdImagePtr im2, int c1, int c2, int *colorMap)
{
	if (!colorMap)
		return c1 == c2;
	if (-2 != colorMap[c1])
		return colorMap[c1] == c2;
	return (colorMap[c1] = gdImageColorExactAlpha (im2, im1->red[c1], im1->green[c1], im1->blue[c1], im1->alpha[c1]))
	       == c2;
}

BGD_DECLARE(void) gdImageGifAnimAddCtx(gdImagePtr im, gdIOCtxPtr out, int LocalCM, int LeftOfs, int TopOfs, int Delay, int Disposal, gdImagePtr previm)
{
	gdImagePtr pim = 0, tim = im;
	int interlace, transparent, BitsPerPixel;
	interlace = im->interlace;
	transparent = im->transparent;

	/* Default is no local color map */
	if (LocalCM < 0) LocalCM = 0;
	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; 
	}
	if (previm) {
		/* create optimized animation.  Compare this image to
		   the previous image and crop the temporary copy of
		   current image to include only changed rectangular
		   area.  Also replace unchanged pixels inside this
		   area with transparent color.  Transparent color
		   needs to be already allocated!
		   Preconditions:
		   TopOfs, LeftOfs are assumed 0

		   Images should be of same size.  If not, a temporary
		   copy is made with the same size as previous image.
		   
		*/
		gdImagePtr prev_pim = 0, prev_tim = previm;
		int x, y;
		int min_x = 0;
		int min_y = tim->sy;
		int max_x = 0;
		int max_y = 0;
		int colorMap[256];

		if (previm->trueColor) {
			prev_pim = gdImageCreatePaletteFromTrueColor(previm, 1, 256);
			if (!prev_pim) {
				return;
			}
			prev_tim = prev_pim; 
		}
		for (x = 0; x < 256; ++x)
			colorMap[x] = -2;

		/* First find bounding box of changed areas. */
		/* first find the top changed row */
		for (y = 0; y < tim->sy; ++y)
			for (x = 0; x < tim->sx; ++x)
				if (!comparewithmap(prev_tim, tim,
						    prev_tim->pixels[y][x],
						    tim->pixels[y][x],
						    colorMap)) {
					min_y = max_y = y;
					min_x = max_x = x;
					goto break_top;
				}
	break_top:
		if (tim->sy == min_y) {
			/* No changes in this frame!! Encode empty image. */
			transparent = 0;
			min_x = min_y = 1;
			max_x = max_y = 0;
		} else {
			/* Then the bottom row */
			for (y = tim->sy - 1; y > min_y; --y)
				for (x = 0; x < tim->sx; ++x)
					if (!comparewithmap
					    (prev_tim, tim,
					     prev_tim->pixels[y][x],
					     tim->pixels[y][x],
					     colorMap)) {
						max_y = y;
						if (x < min_x) min_x = x;
						if (x > max_x) max_x = x;
						goto break_bot;
					}
		break_bot:
			/* left side */
			for (x = 0; x < min_x; ++x)
				for (y = min_y; y <= max_y; ++y)
					if (!comparewithmap
					    (prev_tim, tim,
					     prev_tim->pixels[y][x],
					     tim->pixels[y][x],
					     colorMap)) {
						min_x = x;
						goto break_left;
					}
		break_left:
			/* right side */
			for (x = tim->sx-1; x > max_x; --x)
				for (y = min_y; y <= max_y; ++y)
					if (!comparewithmap
					    (prev_tim, tim,
					     prev_tim->pixels[y][x],
					     tim->pixels[y][x],
					     colorMap)) {
						max_x = x;
						goto break_right;
					}
		break_right:
			;
		}

		LeftOfs = min_x;
		TopOfs = min_y;
		Disposal = 1;

		/* Make a copy of the image with the new offsets.
		   But only if necessary. */
		if (min_x != 0 || max_x != tim->sx-1
		    || min_y != 0 || max_y != tim->sy-1
		    || transparent >= 0) {
			gdImagePtr pim2
				= gdImageCreate(max_x-min_x+1, max_y-min_y+1);
			if (!pim2) {
				if (prev_pim)
					gdImageDestroy (prev_pim);
				goto fail_end;
			}
			gdImagePaletteCopy (pim2, LocalCM ? tim : prev_tim);
			gdImageCopy (pim2, tim, 0, 0, min_x, min_y,