dgif_lib.c

支持各种栅格图像和矢量图像读取的库

/******************************************************************************
*   "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). *
******************************************************************************/


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

#ifdef unix
#include <unistd.h>
#endif

#ifndef __MSDOS__
#include <stdlib.h>
#endif
#include <fcntl.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. */
#define GIF_STAMP	"GIFVER"	 /* First chars in file - GIF stamp. */
#define GIF_STAMP_LEN	sizeof(GIF_STAMP) - 1
#define GIF_VERSION_POS	3		/* Version first character in stamp. */

/* 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, int *Word);
static int DGifSetupDecompress(GifFileType *GifFile);
static int DGifDecompressLine(GifFileType *GifFile, GifPixelType *Line,
								int LineLen);
static int DGifGetPrefixChar(unsigned int *Prefix, int Code, int ClearCode);
static int DGifDecompressInput(GifFileType *GifFile, int *Code);
static int DGifBufferedInput(GifFileType *GifFile, GifByteType *Buf,
						     GifByteType *NextByte);

/******************************************************************************
*   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
#ifdef O_BINARY
			           | O_BINARY
#endif /* __MSDOS__ */
			                     )) == -1) {
	_GifError = D_GIF_ERR_OPEN_FAILED;
	return NULL;
    }

    GifFile = DGifOpenFileHandle(FileHandle);
    if (GifFile == (GifFileType *)NULL)
        close(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)
{
    char Buf[GIF_STAMP_LEN+1];
    GifFileType *GifFile;
    GifFilePrivateType *Private;
    FILE *f;

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

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

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

#if defined(__MSDOS__) || defined(WIN32)
    setmode(FileHandle, O_BINARY);      /* Make sure it is in binary mode. */
    f = fdopen(FileHandle, "rb");           /* Make it into a stream: */
    setvbuf(f, NULL, _IOFBF, GIF_FILE_BUFFER_SIZE);/* And inc. stream buffer.*/
#else
    f = fdopen(FileHandle, "rb");           /* Make it into a stream: */
#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;
}

/******************************************************************************
* GifFileType constructor with user supplied input function (TVT)             *
*                                                                             *
******************************************************************************/
GifFileType *DGifOpen( void* userData, InputFunc readFunc )
{
    char Buf[GIF_STAMP_LEN+1];
    GifFileType *GifFile;
    GifFilePrivateType *Private;


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

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

    if (!(Private = (GifFilePrivateType*) malloc(sizeof(GifFilePrivateType)))){
	  _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);

	/* Get the global color map: */
	for (i = 0; i < GifFile->SColorMap->ColorCount; i++) {
	    if (READ(GifFile, Buf, 3) != 3) {
		_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];
	}
    }

    return GIF_OK;
}

/******************************************************************************
*   This routine should be called before any attemp 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 attemp 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? */

	if (GifFile->Image.ColorMap)
        {
	    FreeMapObject(GifFile->Image.ColorMap);
        }