dgif_lib.c

giflib-4.1.6.tar.gz,最新的GIF 解码库

/******************************************************************************
 *   "Gif-Lib" - Yet another gif library.
 *
 * Written by:  Gershon Elber            IBM PC Ver 1.1,    Aug. 1990
 ******************************************************************************
 * The kernel of the GIF Decoding process can be found here.
 ******************************************************************************
 * History:
 * 16 Jun 89 - Version 1.0 by Gershon Elber.
 *  3 Sep 90 - Version 1.1 by Gershon Elber (Support for Gif89, Unique names).
 *****************************************************************************/

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdlib.h>
#if defined (__MSDOS__) && !defined(__DJGPP__) && !defined(__GNUC__)
#include <io.h>
#include <alloc.h>
#include <sys\stat.h>
#else
#include <sys/types.h>
#include <sys/stat.h>
#endif /* __MSDOS__ */

#ifdef HAVE_IO_H
#include <io.h>
#endif

#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif /* HAVE_FCNTL_H */
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif /* HAVE_UNISTD_H */
#include <stdio.h>
#include <string.h>
#include "gif_lib.h"
#include "gif_lib_private.h"

#define COMMENT_EXT_FUNC_CODE 0xfe  /* Extension function code for
                                       comment. */

/* avoid extra function call in case we use fread (TVT) */
#define READ(_gif,_buf,_len)                                     \
  (((GifFilePrivateType*)_gif->Private)->Read ?                   \
    ((GifFilePrivateType*)_gif->Private)->Read(_gif,_buf,_len) : \
    fread(_buf,1,_len,((GifFilePrivateType*)_gif->Private)->File))

static int DGifGetWord(GifFileType *GifFile, GifWord *Word);
static int DGifSetupDecompress(GifFileType *GifFile);
static int DGifDecompressLine(GifFileType *GifFile, GifPixelType *Line,
                              int LineLen);
static int DGifGetPrefixChar(GifPrefixType *Prefix, int Code, int ClearCode);
static int DGifDecompressInput(GifFileType *GifFile, int *Code);
static int DGifBufferedInput(GifFileType *GifFile, GifByteType *Buf,
                             GifByteType *NextByte);
#ifndef _GBA_NO_FILEIO

/******************************************************************************
 * Open a new gif file for read, given by its name.
 * Returns GifFileType pointer dynamically allocated which serves as the gif
 * info record. _GifError is cleared if succesfull.
 *****************************************************************************/
GifFileType *
DGifOpenFileName(const char *FileName) {
    int FileHandle;
    GifFileType *GifFile;

    if ((FileHandle = open(FileName, O_RDONLY
#if defined(__MSDOS__) || defined(WINDOWS32) || defined(_OPEN_BINARY)
                           | O_BINARY
#endif /* __MSDOS__ || _OPEN_BINARY */
         )) == -1) {
        _GifError = D_GIF_ERR_OPEN_FAILED;
        return NULL;
    }

    GifFile = DGifOpenFileHandle(FileHandle);
    return GifFile;
}

/******************************************************************************
 * Update a new gif file, given its file handle.
 * Returns GifFileType pointer dynamically allocated which serves as the gif
 * info record. _GifError is cleared if succesfull.
 *****************************************************************************/
GifFileType *
DGifOpenFileHandle(int FileHandle) {

    unsigned char Buf[GIF_STAMP_LEN + 1];
    GifFileType *GifFile;
    GifFilePrivateType *Private;
    FILE *f;

    GifFile = (GifFileType *)malloc(sizeof(GifFileType));
    if (GifFile == NULL) {
        _GifError = D_GIF_ERR_NOT_ENOUGH_MEM;
        close(FileHandle);
        return NULL;
    }

    memset(GifFile, '\0', sizeof(GifFileType));

    Private = (GifFilePrivateType *)malloc(sizeof(GifFilePrivateType));
    if (Private == NULL) {
        _GifError = D_GIF_ERR_NOT_ENOUGH_MEM;
        close(FileHandle);
        free((char *)GifFile);
        return NULL;
    }
#if defined(__MSDOS__) || defined(WINDOWS32) || defined(_OPEN_BINARY)
    setmode(FileHandle, O_BINARY);    /* Make sure it is in binary mode. */
#endif /* __MSDOS__ */

    f = fdopen(FileHandle, "rb");    /* Make it into a stream: */

#if defined(__MSDOS__) || defined(WINDOWS32)
    setvbuf(f, NULL, _IOFBF, GIF_FILE_BUFFER_SIZE);    /* And inc. stream
                                                          buffer. */
#endif /* __MSDOS__ */

    GifFile->Private = (VoidPtr)Private;
    Private->FileHandle = FileHandle;
    Private->File = f;
    Private->FileState = FILE_STATE_READ;
    Private->Read = 0;    /* don't use alternate input method (TVT) */
    GifFile->UserData = 0;    /* TVT */

    /* Lets see if this is a GIF file: */
    if (READ(GifFile, Buf, GIF_STAMP_LEN) != GIF_STAMP_LEN) {
        _GifError = D_GIF_ERR_READ_FAILED;
        fclose(f);
        free((char *)Private);
        free((char *)GifFile);
        return NULL;
    }

    /* The GIF Version number is ignored at this time. Maybe we should do
     * something more useful with it.  */
    Buf[GIF_STAMP_LEN] = 0;
    if (strncmp(GIF_STAMP, Buf, GIF_VERSION_POS) != 0) {
        _GifError = D_GIF_ERR_NOT_GIF_FILE;
        fclose(f);
        free((char *)Private);
        free((char *)GifFile);
        return NULL;
    }

    if (DGifGetScreenDesc(GifFile) == GIF_ERROR) {
        fclose(f);
        free((char *)Private);
        free((char *)GifFile);
        return NULL;
    }

    _GifError = 0;

    return GifFile;
}

#endif /* _GBA_NO_FILEIO */

/******************************************************************************
 * GifFileType constructor with user supplied input function (TVT)
 *****************************************************************************/
GifFileType *
DGifOpen(void *userData,
         InputFunc readFunc) {

    unsigned char Buf[GIF_STAMP_LEN + 1];
    GifFileType *GifFile;
    GifFilePrivateType *Private;

    GifFile = (GifFileType *)malloc(sizeof(GifFileType));
    if (GifFile == NULL) {
        _GifError = D_GIF_ERR_NOT_ENOUGH_MEM;
        return NULL;
    }

    memset(GifFile, '\0', sizeof(GifFileType));

    Private = (GifFilePrivateType *)malloc(sizeof(GifFilePrivateType));
    if (!Private) {
        _GifError = D_GIF_ERR_NOT_ENOUGH_MEM;
        free((char *)GifFile);
        return NULL;
    }

    GifFile->Private = (VoidPtr)Private;
    Private->FileHandle = 0;
    Private->File = 0;
    Private->FileState = FILE_STATE_READ;

    Private->Read = readFunc;    /* TVT */
    GifFile->UserData = userData;    /* TVT */

    /* Lets see if this is a GIF file: */
    if (READ(GifFile, Buf, GIF_STAMP_LEN) != GIF_STAMP_LEN) {
        _GifError = D_GIF_ERR_READ_FAILED;
        free((char *)Private);
        free((char *)GifFile);
        return NULL;
    }

    /* The GIF Version number is ignored at this time. Maybe we should do
     * something more useful with it. */
    Buf[GIF_STAMP_LEN] = 0;
    if (strncmp(GIF_STAMP, Buf, GIF_VERSION_POS) != 0) {
        _GifError = D_GIF_ERR_NOT_GIF_FILE;
        free((char *)Private);
        free((char *)GifFile);
        return NULL;
    }

    if (DGifGetScreenDesc(GifFile) == GIF_ERROR) {
        free((char *)Private);
        free((char *)GifFile);
        return NULL;
    }

    _GifError = 0;

    return GifFile;
}

/******************************************************************************
 * This routine should be called before any other DGif calls. Note that
 * this routine is called automatically from DGif file open routines.
 *****************************************************************************/
int
DGifGetScreenDesc(GifFileType * GifFile) {

    int i, BitsPerPixel;
    GifByteType Buf[3];
    GifFilePrivateType *Private = (GifFilePrivateType *)GifFile->Private;

    if (!IS_READABLE(Private)) {
        /* This file was NOT open for reading: */
        _GifError = D_GIF_ERR_NOT_READABLE;
        return GIF_ERROR;
    }

    /* Put the screen descriptor into the file: */
    if (DGifGetWord(GifFile, &GifFile->SWidth) == GIF_ERROR ||
        DGifGetWord(GifFile, &GifFile->SHeight) == GIF_ERROR)
        return GIF_ERROR;

    if (READ(GifFile, Buf, 3) != 3) {
        _GifError = D_GIF_ERR_READ_FAILED;
        return GIF_ERROR;
    }
    GifFile->SColorResolution = (((Buf[0] & 0x70) + 1) >> 4) + 1;
    BitsPerPixel = (Buf[0] & 0x07) + 1;
    GifFile->SBackGroundColor = Buf[1];
    if (Buf[0] & 0x80) {    /* Do we have global color map? */

        GifFile->SColorMap = MakeMapObject(1 << BitsPerPixel, NULL);
        if (GifFile->SColorMap == NULL) {
            _GifError = D_GIF_ERR_NOT_ENOUGH_MEM;
            return GIF_ERROR;
        }

        /* Get the global color map: */
        for (i = 0; i < GifFile->SColorMap->ColorCount; i++) {
            if (READ(GifFile, Buf, 3) != 3) {
                FreeMapObject(GifFile->SColorMap);
                GifFile->SColorMap = NULL;
                _GifError = D_GIF_ERR_READ_FAILED;
                return GIF_ERROR;
            }
            GifFile->SColorMap->Colors[i].Red = Buf[0];
            GifFile->SColorMap->Colors[i].Green = Buf[1];
            GifFile->SColorMap->Colors[i].Blue = Buf[2];
        }
    } else {
        GifFile->SColorMap = NULL;
    }

    return GIF_OK;
}

/******************************************************************************
 * This routine should be called before any attempt to read an image.
 *****************************************************************************/
int
DGifGetRecordType(GifFileType * GifFile,
                  GifRecordType * Type) {

    GifByteType Buf;
    GifFilePrivateType *Private = (GifFilePrivateType *)GifFile->Private;

    if (!IS_READABLE(Private)) {
        /* This file was NOT open for reading: */
        _GifError = D_GIF_ERR_NOT_READABLE;
        return GIF_ERROR;
    }

    if (READ(GifFile, &Buf, 1) != 1) {
        _GifError = D_GIF_ERR_READ_FAILED;
        return GIF_ERROR;
    }

    switch (Buf) {
      case ',':
          *Type = IMAGE_DESC_RECORD_TYPE;
          break;
      case '!':
          *Type = EXTENSION_RECORD_TYPE;
          break;
      case ';':
          *Type = TERMINATE_RECORD_TYPE;
          break;
      default:
          *Type = UNDEFINED_RECORD_TYPE;
          _GifError = D_GIF_ERR_WRONG_RECORD;
          return GIF_ERROR;
    }

    return GIF_OK;
}

/******************************************************************************
 * This routine should be called before any attempt to read an image.
 * Note it is assumed the Image desc. header (',') has been read.
 *****************************************************************************/
int
DGifGetImageDesc(GifFileType * GifFile) {

    int i, BitsPerPixel;
    GifByteType Buf[3];
    GifFilePrivateType *Private = (GifFilePrivateType *)GifFile->Private;
    SavedImage *sp;

    if (!IS_READABLE(Private)) {
        /* This file was NOT open for reading: */
        _GifError = D_GIF_ERR_NOT_READABLE;
        return GIF_ERROR;
    }

    if (DGifGetWord(GifFile, &GifFile->Image.Left) == GIF_ERROR ||
        DGifGetWord(GifFile, &GifFile->Image.Top) == GIF_ERROR ||
        DGifGetWord(GifFile, &GifFile->Image.Width) == GIF_ERROR ||
        DGifGetWord(GifFile, &GifFile->Image.Height) == GIF_ERROR)
        return GIF_ERROR;
    if (READ(GifFile, Buf, 1) != 1) {
        _GifError = D_GIF_ERR_READ_FAILED;
        return GIF_ERROR;
    }
    BitsPerPixel = (Buf[0] & 0x07) + 1;
    GifFile->Image.Interlace = (Buf[0] & 0x40);
    if (Buf[0] & 0x80) {    /* Does this image have local color map? */

        /*** FIXME: Why do we check both of these in order to do this? 
         * Why do we have both Image and SavedImages? */
        if (GifFile->Image.ColorMap && GifFile->SavedImages == NULL)
            FreeMapObject(GifFile->Image.ColorMap);

        GifFile->Image.ColorMap = MakeMapObject(1 << BitsPerPixel, NULL);
        if (GifFile->Image.ColorMap == NULL) {
            _GifError = D_GIF_ERR_NOT_ENOUGH_MEM;
            return GIF_ERROR;
        }

        /* Get the image local color map: */
        for (i = 0; i < GifFile->Image.ColorMap->ColorCount; i++) {