gif.c

gif图像文件软件解码器的arm版本的源代码程序

///////////////////////////////////////////////////////////////////////////////
//
//  gif.c
//
//  DESCRIPTION
//        Define gif decoding functions
//
//
///////////////////////////////////////////////////////////////////////////////

/*
  Include declarations.
*/

#include "gifcommon.h"
#include "SP_include.h"

#define BitSet(byte,bit)  (((byte) & (bit)) == (bit))
#define LSBFirstOrder(x,y)  (((y) << 8) | (x))

/*
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%   D e c o d e I m a g e                                                     %
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%
%  Method DecodeImage uncompresses an image via GIF-coding.
%
%  The format of the DecodeImage method is:
%
%      unsigned int DecodeImage(Image *image,const long opacity)
%
%  A description of each parameter follows:
%
%    o status:  Method DecodeImage returns True if all the pixels are
%      uncompressed without error, otherwise False.
%
%    o image: The address of a structure of type Image.
%
%    o opacity:  The colormap index associated with the transparent
%      color.
%
%
*/
extern unsigned int DecodeGIFImage
(
    Image           *image,
    const long      opacity,
    OP_BOOLEAN      func(OP_UINT16 x, OP_UINT16 y)
);

extern unsigned int skip_decoding_datablock
(
    Image           *image
);

/*
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+  R e a d B l o b B l o c k                                                  %
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%
%  Method ReadBlobBlock reads data from the image file and returns it.  The
%  amount of data is determined by first reading a count byte.  The number
%  or bytes read is returned.
%
%  The format of the ReadBlobBlock method is:
%
%      unsigned int ReadBlobBlock(Image *image,unsigned char *data)
%
%  A description of each parameter follows:
%
%    o count:  Method ReadBlobBlock returns the number of bytes read.
%
%    o image: The image.
%
%    o data:  Specifies an area to place the information requested from
%      the file.
%
%
*/
unsigned int ReadBlobBlock
(
    Image           *image,
    unsigned char   **data
)
{
    size_t          count;
    unsigned char   *block_count;

    count = ReadBlob(image, 1, &block_count);
    
    if (count == 0)
    {
        return(0);
    }
    return(ReadBlob(image, *block_count, data));
}


// global variables
// global colormap
static unsigned char *global_colormap;
// number of global colors
static unsigned int global_colors;
// image count 
static unsigned int image_count;
// display delay in ms
static unsigned int delay;
// how to dispose the image;
static unsigned int dispose;
// number of iterations
static unsigned int iterations;
// opacity
static long opacity;  
// background
static unsigned char background; 
// flag
static unsigned char flag;  
/* transparent flag */
static OP_BOOLEAN trans_flag = OP_FALSE;

/*
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%   R e a d G I F F r a m e                                                   %
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*/
Image *ReadGIFFrame
(
    Image               *image, 
    unsigned char       *outbuf,
    ImageSaveMethod     saveimage, 
    OP_BOOLEAN          skipdecoding, 
    OP_BOOLEAN          only_info, 
    OP_BOOLEAN          func(OP_UINT16 x, OP_UINT16 y)
)
{

    unsigned char             c;
    unsigned char             *header;
    unsigned char             *tp;
    unsigned char             **pp;
    register unsigned char    *p;

    int                       status;
    unsigned int              count;
    register long             i;
    Image                     *inputimage;

    // save image pointer
    inputimage = image;
    pp = &tp;

    for( ; ; )
    {
        count = ReadBlob(image, 1, pp);
        c = (*pp)[0];
        
        if (count == 0)
        {
            break;
        }
        if (c == ';')   /* 0x3B */
        {
            break;  /* terminator */
        }
        if (c == '!')   /* 0x21 */
        {
            /*
              GIF Extension block.
            */
            count=ReadBlob(image, 1, pp);
            c = (*pp)[0];
            
            if (count == 0)
            {
                /* 
                * added DestoryImage because of 
                * remove the free momery routine in gifDecodeImage()
                */
                if ( image->next != OP_NULL )
                {
                    DestroyImage(image->next);
                    op_debug_msg(SP_DEBUG_GROUP_MMI, DEBUG_HIGH, "Image Decoder DestoryImage() in count == 0 \n" );
                }

                if(image != inputimage) 
                {
                    DestroyImage(image);
                }
                return OP_NULL;
            }
            switch (c)
            {

                /* 
                  The Graphics Control Extension contains parameters used 
                  when procssing a graphic rendering block.
                  The scope of this extension is the first graphic rendering block to follow.
                  The extension contains only one data sub-block.
                */
                case 0xf9:
                {
                    /*
                      Read Graphics Control extension.
                    */
                    while (ReadBlobBlock(image, pp) != 0);
                    header = *pp;
                    dispose = header[0] >> 2;
                    delay = (header[2] << 8) | header[1];
                    if ((header[0] & 0x01) == 1)
                    {
                        trans_flag = OP_TRUE;
                        opacity = header[3];
                    }
                    else
                    {
                        trans_flag = OP_FALSE;
                    }
                    break;
                }
                case 0xfe:
                {
                    /* 
                    * remove to related comments code because violation of memory access 
                    * char    *comments;
                    */

                    /* Read Comment extension. */
                    /*
                    * remove to related comments code because violation of memory access 
                    * comments = AllocateString((char *) OP_NULL, image->getmemory);
                    */

                    for ( ; ; )
                    {
                        count = ReadBlobBlock(image,pp);
                        /* 
                        * remove to related comments code because violation of memory access 
                        * header = *pp;
                        */
                        if (count == 0)
                        {
                            break;
                        }
                        /* 
                        * remove to related comments code because violation of memory access 
                        * header[count] = '\0';
                        * (void) ConcatenateString(&comments, (const char *) header, 
                        *          image->getmemory, image->freememory);
                        */
                    }
                    /* 
                    * remove to related comments code because violation of memory access 
                    * (void) SetImageAttribute(image, "comment", comments);
                    * image->freememory((void *) comments);
                    */
                    break;
                }