/*** $Id: gif.c,v 1.7 2003/09/04 06:02:53 weiym Exp $** ** gif.c: Low-level GIF file read/save routines.** ** Copyright (C) 2003 Feynman Software.** Copyright (C) 2000, 2001 Wei Yongming**** Current maintainer: Wei Yongming**** Create date: 2000/08/29*//*** This program is free software; you can redistribute it and/or modify** it under the terms of the GNU General Public License as published by** the Free Software Foundation; either version 2 of the License, or** (at your option) any later version.**** This program is distributed in the hope that it will be useful,** but WITHOUT ANY WARRANTY; without even the implied warranty of** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the** GNU General Public License for more details.**** You should have received a copy of the GNU General Public License** along with this program; if not, write to the Free Software** Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA*//* Code for GIF decoding has been adapted from XPaint:                   *//* +-------------------------------------------------------------------+ *//* | Copyright 1990, 1991, 1993 David Koblas.                          | *//* | Copyright 1996 Torsten Martinsen.                                 | *//* |   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.           | *//* +-------------------------------------------------------------------+ *//* Portions Copyright (C) 1999 Sam Lantinga *//* Portions Copyright (C) 2000, 2001 Wei Yongming *//* Adapted for use in SDL by Sam Lantinga -- 7/20/1998 *//* Adapted for use in MiniGUI by Wei Yongming -- 8/30/2000 *//* Adapted for Big Endian system by Wei Yongming -- 2001-11-13 */#include <stdio.h>#include <stdlib.h>#include <string.h>#include "common.h"#include "gdi.h"#include "readbmp.h"#ifdef _GIF_FILE_SUPPORT/* * GIF decoding routine */#define MAXCOLORMAPSIZE         256#define MAX_LWZ_BITS            12#define INTERLACE               0x40#define LOCALCOLORMAP           0x80#define CM_RED                  0#define CM_GREEN                1#define CM_BLUE                 2#define BitSet(byte, bit)              (((byte) & (bit)) == (bit))#define ReadOK(file,buffer,len)        MGUI_RWread(file, buffer, len, 1)#define LM_to_uint(a,b)                (((b)<<8)|(a))struct {    unsigned int Width;    unsigned int Height;    unsigned char ColorMap[3][MAXCOLORMAPSIZE];    unsigned int BitPixel;    unsigned int ColorResolution;    unsigned int Background;    unsigned int AspectRatio;    int GrayScale;} GifScreen;static struct {    int transparent;    int delayTime;    int inputFlag;    int disposal;} Gif89;static int ReadColorMap(MG_RWops* src, int number,                unsigned char buffer[3][MAXCOLORMAPSIZE], int *flag);static int DoExtension(MG_RWops* src, int label);static int GetDataBlock(MG_RWops* src, unsigned char *buf);static int GetCode(MG_RWops* src, int code_size, int flag);static int LWZReadByte(MG_RWops* src, int flag, int input_code_size);static int ReadImage(MG_RWops* src, MYBITMAP* bmp, RGB* pal, int len, int height, int,                unsigned char cmap[3][MAXCOLORMAPSIZE],                int gray, int interlace, int ignore);int load_gif (MG_RWops *src, MYBITMAP* bmp, RGB* pal){    unsigned char buf[16];    unsigned char c;    unsigned char localColorMap[3][MAXCOLORMAPSIZE];    int grayScale;    int useGlobalColormap;    int bitPixel;    int imageCount = 0;    char version[4];    int imageNumber = 1;    int ok = 0;    if (!ReadOK (src, buf, 6))        return ERR_BMP_IMAGE_TYPE;                /* not gif image*/    if (strncmp((char *) buf, "GIF", 3) != 0)        return ERR_BMP_IMAGE_TYPE;    strncpy (version, (char *) buf + 3, 3);    version [3] = '\0';    if (strcmp(version, "87a") != 0 && strcmp(version, "89a") != 0) {#ifdef _DEBUG        fprintf (stderr, "load_gif: GIF version number is not 87a or 89a\n");#endif        return ERR_BMP_NOT_SUPPORTED;                /* image loading error*/    }    Gif89.transparent = -1;    Gif89.delayTime = -1;    Gif89.inputFlag = -1;    Gif89.disposal = 0;    if (!ReadOK (src, buf, 7)) {#ifdef _DEBUG        fprintf (stderr, "load_gif: bad screen descriptor\n");#endif        return ERR_BMP_LOAD;                /* image loading error*/    }    GifScreen.Width = LM_to_uint (buf[0], buf[1]);    GifScreen.Height = LM_to_uint (buf[2], buf[3]);    GifScreen.BitPixel = 2 << (buf[4] & 0x07);    GifScreen.ColorResolution = (((buf[4] & 0x70) >> 3) + 1);    GifScreen.Background = buf[5];    GifScreen.AspectRatio = buf[6];    if (BitSet(buf[4], LOCALCOLORMAP)) {        /* Global Colormap */        if (ReadColorMap(src, GifScreen.BitPixel, GifScreen.ColorMap,                         &GifScreen.GrayScale)) {#ifdef _DEBUG            fprintf (stderr, "load_gif: bad global colormap\n");#endif            return ERR_BMP_LOAD;                /* image loading error*/        }    }    do {        if (!ReadOK (src, &c, 1)) {#ifdef _DEBUG            fprintf (stderr, "load_gif: EOF on image data\n");#endif            goto done;        }        if (c == ';') {                /* GIF terminator */            if (imageCount < imageNumber) {#ifdef _DEBUG                fprintf (stderr, "load_gif: no image %d of %d\n", imageNumber,imageCount);#endif                goto done;            }        }        if (c == '!') {                /* Extension */            if (!ReadOK (src, &c, 1)) {#ifdef _DEBUG                fprintf (stderr, "load_gif: EOF on extension function code\n");#endif                goto done;            }            DoExtension (src, c);            continue;        }        if (c != ',') {                /* Not a valid start character */            continue;        }        ++imageCount;        if (!ReadOK (src, buf, 9)) {#ifdef _DEBUG            fprintf (stderr, "load_gif: bad image size\n");#endif            goto done;        }        useGlobalColormap = !BitSet (buf[8], LOCALCOLORMAP);        bitPixel = 1 << ((buf[8] & 0x07) + 1);        if (!useGlobalColormap) {            if (ReadColorMap(src, bitPixel, localColorMap, &grayScale)) {#ifdef _DEBUG                fprintf (stderr, "load_gif: bad local colormap\n");#endif                goto done;            }            ok = ReadImage (src, bmp, pal, LM_to_uint(buf[4], buf[5]),                              LM_to_uint(buf[6], buf[7]),                              bitPixel, localColorMap, grayScale,                              BitSet(buf[8], INTERLACE),                              imageCount != imageNumber);        } else {            ok = ReadImage(src, bmp, pal, LM_to_uint(buf[4], buf[5]),                              LM_to_uint(buf[6], buf[7]),                              GifScreen.BitPixel, GifScreen.ColorMap,                              GifScreen.GrayScale, BitSet(buf[8], INTERLACE),                              imageCount != imageNumber);        }    } while (ok == 0);    bmp->flags = MYBMP_FLOW_DOWN;    if ( Gif89.transparent > 0 ) {        bmp->flags |= MYBMP_TRANSPARENT;        bmp->transparent = Gif89.transparent;    }    if(ok)            return 0;                /* image load ok*/done:    return ERR_BMP_LOAD;                        /* image load error*/}static intReadColorMap (MG_RWops *src, int number, unsigned char buffer[3][MAXCOLORMAPSIZE],    int *gray){    int i;    unsigned char rgb[3];    int flag;    flag = TRUE;    for (i = 0; i < number; ++i) {        if (!ReadOK(src, rgb, sizeof(rgb)))            return 1;        buffer[CM_RED][i] = rgb[0];        buffer[CM_GREEN][i] = rgb[1];        buffer[CM_BLUE][i] = rgb[2];        flag &= (rgb[0] == rgb[1] && rgb[1] == rgb[2]);    }#if 0    if (flag)        *gray = (number == 2) ? PBM_TYPE : PGM_TYPE;    else        *gray = PPM_TYPE;#else    *gray = 0;#endif    return FALSE;}static intDoExtension(MG_RWops *src, int label){    static unsigned char buf[256];    switch (label) {    case 0x01:                        /* Plain Text Extension */        break;    case 0xff:                        /* Application Extension */        break;    case 0xfe:                        /* Comment Extension */        while (GetDataBlock(src, (unsigned char *) buf) != 0);        return FALSE;    case 0xf9:                        /* Graphic Control Extension */        GetDataBlock(src, (unsigned char *) buf);        Gif89.disposal = (buf[0] >> 2) & 0x7;        Gif89.inputFlag = (buf[0] >> 1) & 0x1;        Gif89.delayTime = LM_to_uint(buf[1], buf[2]);        if ((buf[0] & 0x1) != 0)            Gif89.transparent = buf[3];        while (GetDataBlock(src, (unsigned char *) buf) != 0);        return FALSE;    default:        break;    }