gif.c

gif图像文件软件解码器的arm版本的源代码程序

                /*
                  The Application Extension contains application-specific information; 
                  it conforms with the extension block syntax, as described below, 
                  and its block label is 0xFF.
                */
                case 0xff:
                {
                    int   loop;
        
                    /*
                      Read Netscape Loop extension.
                    */
                    loop = OP_FALSE;
                    if (ReadBlobBlock(image, pp) != 0)
                    {
                        header = *pp;
                        loop = !LocaleNCompare((char *) header, "NETSCAPE2.0", 11);
                    }
                    while (ReadBlobBlock(image, pp) != 0)
                    {
                        header = *pp;
                        if (loop)
                        {
                            iterations = (header[2] << 8) | header[1];
                        }
                    }
                    break;
                }
                default:
                {
                    while (ReadBlobBlock(image, pp) != 0) header = *pp;
                    break;
                }
            }
        }
        if (c != ',')   /* 0x2C */
        {
            continue;
        }
        if (image_count != 0)
        {
            /*
              Allocate next image structure.
            */
            AllocateNextImage(image);
            if (image->next == (Image *) OP_NULL)
            {
                return((Image *) OP_NULL);
            }
            image = image->next;
        }
        image_count++;
        /*
          Read image attributes.
        */
        image->page.x = ReadBlobLSBShort(image);
        image->page.y = ReadBlobLSBShort(image);
        image->columns = ReadBlobLSBShort(image);
        image->rows = ReadBlobLSBShort(image);
        image->depth = 8;
        flag = ReadBlobByte(image);
        image->interlace = BitSet(flag,0x40) ? PlaneInterlace : NoInterlace;
        image->colors = !BitSet(flag,0x80) ? global_colors : 1 << ((flag & 0x07)+1);

        if (opacity >= (long) image->colors)
        {
            image->colors = opacity+1;
        }

        image->trans_flag = trans_flag;
        image->delay = delay;
        image->dispose = dispose;
        image->iterations = iterations;
        image->matte = opacity >= 0;
        delay = 0;
        dispose = 0;

        if ((image->columns == 0) || (image->rows == 0))
        {
            if(image != inputimage)
            {
                DestroyImage(image);
            }
            return OP_NULL;
        }

        image->pixeldata = (PixelPacket *)outbuf;

        /*
          Inititialize colormap.
        */
        if (!AllocateImageColormap(image, image->colors))
        {
            if(image != inputimage)
            {
                DestroyImage(image);
            }
            return OP_NULL;
        }

        if (!BitSet(flag, 0x80))
        {
            /*
              Use global colormap.
            */
            p = global_colormap;
            for (i=0; i < (long) image->colors; i++)
            {
                image->colormap[i].red = Upscale(*p++);
                image->colormap[i].green = Upscale(*p++);
                image->colormap[i].blue = Upscale(*p++);
            }
            image->background_color = image->colormap[Min(background, image->colors-1)];
        }
        else
        {
            /*
              Read local colormap.
            */
            (void) ReadBlob(image, 3*image->colors, pp);
            p = *pp;
            for (i=0; i < (long) image->colors; i++)
            {
                image->colormap[i].red = Upscale(*p++);
                image->colormap[i].green = Upscale(*p++);
                image->colormap[i].blue = Upscale(*p++);
            }
        }

        /*
          Decode image.
        */
        /* decide if we need to decode */
        if(!skipdecoding)
        {
            status = DecodeGIFImage(image,opacity,func);
            if (status == OP_FALSE)
            {
                if(image != inputimage)
                {
                    DestroyImage(image);
                }
                return OP_NULL;
            }
            if(saveimage != OP_NULL) 
            {
                saveimage(image);
            }
        }
        else if (only_info)
        {
            status = skip_decoding_datablock(image);
            if (status == OP_FALSE)
            {
                if(image != inputimage)
                {
                    DestroyImage(image);
                }
                return OP_NULL;
            }
        }
        return(image);
    }

    /* 
    * 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 ReadGIFFrame() \n" );
    }

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

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%   R e a d G I F H e a d e r                                                 %
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
*/
Image *ReadGIFHeader
(
    const Image     *image_info
)
{
    unsigned char     c;
    unsigned char     *magick;
    unsigned char     *tp;
    unsigned char     **pp;
    unsigned int      count;
    int               status;
    Image             *image;



    pp = &tp;
    /*
    Open image file.
    */
    image = AllocateImage(image_info);

    /* 
      Investigate about status(OpenBlob()) routine
      Always return OP_TRUE now in the OpenBlob().
    */

    status = OpenBlob(image, ReadBinaryType);
    if (status == OP_FALSE)
    {
        DestroyImage(image);
        return OP_NULL;
    }
    

    /* 
      6 -> for read the file format(GIF87a or GIF89a -> first six character)
      Determine if this is a GIF file.
    */
    count = ReadBlob(image, 6, pp);
    magick = *pp;

    /* Neither GIF87, GIF89 */
    if ((count == 0) || ((LocaleNCompare((char *) magick,"GIF87",5) != 0) &&
            (LocaleNCompare((char *) magick,"GIF89",5) != 0)))
    {
        DestroyImage(image);
        return OP_NULL;
    }
    global_colors = 0;
    global_colormap = (unsigned char *) OP_NULL;
    image->page.width = ReadBlobLSBShort(image);
    image->page.height = ReadBlobLSBShort(image);
    flag = ReadBlobByte(image);

    /* background -> background color num of image in file */
    background = ReadBlobByte(image);

    c = ReadBlobByte(image);  /* reserved */

    /* c -> only GIF89a, c != 0 -> ratio of width and height (c+15)/64 */

    /* 
      (flag & 0x07)+1 -> bit num of pallete
      (1<<(flag>>4)+1) -> color bit num of source image
    */

    global_colors = 1 << ((flag & 0x07)+1);
    if (BitSet(flag, 0x80))
    {
        (void) ReadBlob(image, 3*global_colors, pp);
        global_colormap = *pp;
    }
    delay = 0;
    dispose = 0;
    iterations = 0;
    opacity = (-1);
    image_count = 0;
    trans_flag = OP_FALSE;

    return image;
}