egif_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                Ver 1.1, Aug. 1990
 ******************************************************************************
 * The kernel of the GIF Encoding process can be found here.
 ******************************************************************************
 * History:
 * 14 Jun 89 - Version 1.0 by Gershon Elber.
 *  3 Sep 90 - Version 1.1 by Gershon Elber (Support for Gif89, Unique names).
 * 26 Jun 96 - Version 3.0 by Eric S. Raymond (Full GIF89 support)
 *****************************************************************************/

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

/* Find a thirty-two bit int type */
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_STDINT_H
#include <stdint.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_INTTYPES_H
#include <inttypes.h>
#endif

#ifdef __MSDOS__
#include <io.h>
#include <alloc.h>
#include <sys\stat.h>
#else
#include <sys/types.h>
#include <sys/stat.h>
#ifdef R6000

/* FIXME: What is sys/mode.h?  Can we substitute a check for this file rather
 * than a check based on machine type?
 */
#include <sys/mode.h>
#endif
#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 <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "gif_lib.h"
#include "gif_lib_private.h"

/* #define DEBUG_NO_PREFIX                  Dump only compressed data. */

/* Masks given codes to BitsPerPixel, to make sure all codes are in range: */
static GifPixelType CodeMask[] = {
    0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff
};

static char GifVersionPrefix[GIF_STAMP_LEN + 1] = GIF87_STAMP;

#define WRITE(_gif,_buf,_len)   \
  (((GifFilePrivateType*)_gif->Private)->Write ?    \
   ((GifFilePrivateType*)_gif->Private)->Write(_gif,_buf,_len) :    \
   fwrite(_buf, 1, _len, ((GifFilePrivateType*)_gif->Private)->File))

static int EGifPutWord(int Word, GifFileType * GifFile);
static int EGifSetupCompress(GifFileType * GifFile);
static int EGifCompressLine(GifFileType * GifFile, GifPixelType * Line,
                            int LineLen);
static int EGifCompressOutput(GifFileType * GifFile, int Code);
static int EGifBufferedOutput(GifFileType * GifFile, GifByteType * Buf,
                              int c);

/******************************************************************************
 * Open a new gif file for write, given by its name. If TestExistance then
 * if the file exists this routines fails (returns NULL).
 * Returns GifFileType pointer dynamically allocated which serves as the gif
 * info record. _GifError is cleared if succesfull.
 *****************************************************************************/
GifFileType *
EGifOpenFileName(const char *FileName,
                 int TestExistance) {

    int FileHandle;
    GifFileType *GifFile;

    if (TestExistance)
        FileHandle = open(FileName, O_WRONLY | O_CREAT | O_EXCL
#if defined(__MSDOS__) || defined(WINDOWS32) || defined(_OPEN_BINARY)
                          | O_BINARY
#endif /* __MSDOS__ */
                          , S_IREAD | S_IWRITE);
    else
        FileHandle = open(FileName, O_WRONLY | O_CREAT | O_TRUNC
#if defined(__MSDOS__) || defined(WINDOWS32) || defined(_OPEN_BINARY)
                          | O_BINARY
#endif /* __MSDOS__ */
                          , S_IREAD | S_IWRITE);

    if (FileHandle == -1) {
        _GifError = E_GIF_ERR_OPEN_FAILED;
        return NULL;
    }
    GifFile = EGifOpenFileHandle(FileHandle);
    if (GifFile == (GifFileType *) NULL)
        close(FileHandle);
    return GifFile;
}

/******************************************************************************
 * Update a new gif file, given its file handle, which must be opened for
 * write in binary mode.
 * Returns GifFileType pointer dynamically allocated which serves as the gif
 * info record. _GifError is cleared if succesfull.
 *****************************************************************************/
GifFileType *
EGifOpenFileHandle(int FileHandle) {

    GifFileType *GifFile;
    GifFilePrivateType *Private;
    FILE *f;

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

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

    Private = (GifFilePrivateType *)malloc(sizeof(GifFilePrivateType));
    if (Private == NULL) {
        free(GifFile);
        _GifError = E_GIF_ERR_NOT_ENOUGH_MEM;
        return NULL;
    }
    if ((Private->HashTable = _InitHashTable()) == NULL) {
        free(GifFile);
        free(Private);
        _GifError = E_GIF_ERR_NOT_ENOUGH_MEM;
        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, "wb");    /* 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_WRITE;

    Private->Write = (OutputFunc) 0;    /* No user write routine (MRB) */
    GifFile->UserData = (VoidPtr) 0;    /* No user write handle (MRB) */

    _GifError = 0;

    return GifFile;
}

/******************************************************************************
 * Output constructor that takes user supplied output function.
 * Basically just a copy of EGifOpenFileHandle. (MRB)
 *****************************************************************************/
GifFileType *
EGifOpen(void *userData,
         OutputFunc writeFunc) {

    GifFileType *GifFile;
    GifFilePrivateType *Private;

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

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

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

    Private->HashTable = _InitHashTable();
    if (Private->HashTable == NULL) {
        free (GifFile);
        free (Private);
        _GifError = E_GIF_ERR_NOT_ENOUGH_MEM;
        return NULL;
    }

    GifFile->Private = (VoidPtr) Private;
    Private->FileHandle = 0;
    Private->File = (FILE *) 0;
    Private->FileState = FILE_STATE_WRITE;

    Private->Write = writeFunc;    /* User write routine (MRB) */
    GifFile->UserData = userData;    /* User write handle (MRB) */

    _GifError = 0;

    return GifFile;
}

/******************************************************************************
 * Routine to set current GIF version. All files open for write will be
 * using this version until next call to this routine. Version consists of
 * 3 characters as "87a" or "89a". No test is made to validate the version.
 *****************************************************************************/
void
EGifSetGifVersion(const char *Version) {
    strncpy(GifVersionPrefix + GIF_VERSION_POS, Version, 3);
}

/******************************************************************************
 * This routine should be called before any other EGif calls, immediately
 * follows the GIF file openning.
 *****************************************************************************/
int
EGifPutScreenDesc(GifFileType * GifFile,
                  int Width,
                  int Height,
                  int ColorRes,
                  int BackGround,
                  const ColorMapObject * ColorMap) {

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

    if (Private->FileState & FILE_STATE_SCREEN) {
        /* If already has screen descriptor - something is wrong! */
        _GifError = E_GIF_ERR_HAS_SCRN_DSCR;
        return GIF_ERROR;
    }
    if (!IS_WRITEABLE(Private)) {
        /* This file was NOT open for writing: */
        _GifError = E_GIF_ERR_NOT_WRITEABLE;
        return GIF_ERROR;
    }

/* First write the version prefix into the file. */
#ifndef DEBUG_NO_PREFIX
    if (WRITE(GifFile, (unsigned char *)GifVersionPrefix,
              strlen(GifVersionPrefix)) != strlen(GifVersionPrefix)) {
        _GifError = E_GIF_ERR_WRITE_FAILED;
        return GIF_ERROR;
    }
#endif /* DEBUG_NO_PREFIX */

    GifFile->SWidth = Width;
    GifFile->SHeight = Height;
    GifFile->SColorResolution = ColorRes;
    GifFile->SBackGroundColor = BackGround;
    if (ColorMap) {
        GifFile->SColorMap = MakeMapObject(ColorMap->ColorCount,
                                           ColorMap->Colors);
        if (GifFile->SColorMap == NULL) {
            _GifError = E_GIF_ERR_NOT_ENOUGH_MEM;
            return GIF_ERROR;
        }
    } else
        GifFile->SColorMap = NULL;

    /*
     * Put the logical screen descriptor into the file:
     */
    /* Logical Screen Descriptor: Dimensions */
    EGifPutWord(Width, GifFile);
    EGifPutWord(Height, GifFile);

    /* Logical Screen Descriptor: Packed Fields */
    /* Note: We have actual size of the color table default to the largest
     * possible size (7+1 == 8 bits) because the decoder can use it to decide
     * how to display the files.
     */
    Buf[0] = (ColorMap ? 0x80 : 0x00) | /* Yes/no global colormap */
             ((ColorRes - 1) << 4) | /* Bits allocated to each primary color */
        (ColorMap ? ColorMap->BitsPerPixel - 1 : 0x07 ); /* Actual size of the
                                                            color table. */
    Buf[1] = BackGround;    /* Index into the ColorTable for background color */
    Buf[2] = 0;             /* Pixel Aspect Ratio */
#ifndef DEBUG_NO_PREFIX
    WRITE(GifFile, Buf, 3);
#endif /* DEBUG_NO_PREFIX */

    /* If we have Global color map - dump it also: */
#ifndef DEBUG_NO_PREFIX
    if (ColorMap != NULL)
        for (i = 0; i < ColorMap->ColorCount; i++) {
            /* Put the ColorMap out also: */
            Buf[0] = ColorMap->Colors[i].Red;
            Buf[1] = ColorMap->Colors[i].Green;
            Buf[2] = ColorMap->Colors[i].Blue;
            if (WRITE(GifFile, Buf, 3) != 3) {
                _GifError = E_GIF_ERR_WRITE_FAILED;
                return GIF_ERROR;
            }
        }
#endif /* DEBUG_NO_PREFIX */

    /* Mark this file as has screen descriptor, and no pixel written yet: */
    Private->FileState |= FILE_STATE_SCREEN;

    return GIF_OK;
}

/******************************************************************************
 * This routine should be called before any attempt to dump an image - any
 * call to any of the pixel dump routines.
 *****************************************************************************/
int
EGifPutImageDesc(GifFileType * GifFile,
                 int Left,
                 int Top,
                 int Width,
                 int Height,
                 int Interlace,
                 const ColorMapObject * ColorMap) {

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

    if (Private->FileState & FILE_STATE_IMAGE &&
#if defined(__MSDOS__) || defined(WINDOWS32) || defined(__GNUC__)
        Private->PixelCount > 0xffff0000UL) {
#else
        Private->PixelCount > 0xffff0000) {
#endif /* __MSDOS__ */
        /* If already has active image descriptor - something is wrong! */
        _GifError = E_GIF_ERR_HAS_IMAG_DSCR;
        return GIF_ERROR;
    }
    if (!IS_WRITEABLE(Private)) {
        /* This file was NOT open for writing: */
        _GifError = E_GIF_ERR_NOT_WRITEABLE;
        return GIF_ERROR;
    }
    GifFile->Image.Left = Left;
    GifFile->Image.Top = Top;
    GifFile->Image.Width = Width;
    GifFile->Image.Height = Height;
    GifFile->Image.Interlace = Interlace;
    if (ColorMap) {
        GifFile->Image.ColorMap = MakeMapObject(ColorMap->ColorCount,
                                                ColorMap->Colors);
        if (GifFile->Image.ColorMap == NULL) {
            _GifError = E_GIF_ERR_NOT_ENOUGH_MEM;