利用FreeImage将gif图像转为opencv中的Mat

网上有将gif转为iplimg的版本，只是用惯了C++的接口，所以就写了个转Mat的版本，代码比较简单

一、读文件

 1     int MatFun::gif2Mat(char* data, size_t dataSize, vector<Mat>& gifImgs, Mat& singleImg)
 2     {
 3         /* initialise
 4         ->open memory
 5         ->getImageType
 6         ->load bitmaps
 7         ->bitmaps to Mat
 8         ->free all resource
 9         */
10         // condition1: data is not null
11         if (NULL == data || dataSize == 0)
12             return -1;
13         FreeImage_Initialise();
14         FIMEMORY* memory = FreeImage_OpenMemory((BYTE*)data, dataSize);
15         if (NULL==memory)
16         {
17             FreeImage_DeInitialise();   //condition 2: memory is not null
18         }
19
20         FREE_IMAGE_FORMAT fif = FreeImage_GetFileTypeFromMemory(memory);
21         if (FIF_UNKNOWN == fif)    //condition 3: type of image should be know
22         {
23             fprintf(stderr, "unknown type of image");
24             if (NULL != memory) FreeImage_CloseMemory(memory);
25             FreeImage_DeInitialise();
26             return -1;
27         }
28         else if (FIF_GIF != fif)  //condition 4: type of image should be GIF
29         {
30             if (NULL != memory) FreeImage_CloseMemory(memory);
31             FreeImage_DeInitialise();
32             return 0;
33         }
34
35         FIMULTIBITMAP * fiBmp = FreeImage_LoadMultiBitmapFromMemory(fif, memory, GIF_DEFAULT);
36         if (NULL==fiBmp)
37         {
38             if (NULL != memory) FreeImage_CloseMemory(memory);   //condition 5: bitmaps is not null
39             FreeImage_DeInitialise();
40             return -1;
41         }
42
43         int num = FreeImage_GetPageCount(fiBmp);
44
45         for (int i = 0; i < num; i++)
46         {
47             if (i==0 || i==2)
48             {
49                 FIBITMAP *mfibmp = FreeImage_LockPage(fiBmp, i);
50                 if (mfibmp)
51                 {
52                     Mat dst = bitMap2Mat(mfibmp, fif);
53                     FreeImage_UnlockPage(fiBmp, mfibmp, false);
54                     if (dst.empty())
55                     {
56                         if (NULL != memory) FreeImage_CloseMemory(memory);
57                         if (NULL != fiBmp) FreeImage_CloseMultiBitmap(fiBmp, GIF_DEFAULT);
58                         FreeImage_DeInitialise();
59                         return -1;
60                     }
61                     gifImgs.push_back(dst);
62                     dst.release();
63                 }
64             }
65         }
66
67         if (NULL != memory)
68             FreeImage_CloseMemory(memory);
69         if (NULL != fiBmp)
70             FreeImage_CloseMultiBitmap(fiBmp);
71         FreeImage_DeInitialise();
72
73         return 0;
74     }

这部分其实功能很简单，代码里面大部分都是检查，实际执行就初始化、打开内存、内存中读bitmap这几步。

二、gif转Mat

    Mat MatFun::bitMap2Mat(FIBITMAP* fiBmp, const FREE_IMAGE_FORMAT &fif)
    {
        if (NULL == fiBmp || FIF_GIF != fif)
            return Mat();
        int width = FreeImage_GetWidth(fiBmp);
        int height = FreeImage_GetHeight(fiBmp);

        BYTE intensity;
        BYTE* pIntensity = &intensity;
        if(FreeImage_GetBPP(fiBmp) !=8)
            fiBmp = FreeImage_ConvertTo8Bits(fiBmp); //必须转化为8bit
        RGBQUAD* pixels = new RGBQUAD;
        pixels = FreeImage_GetPalette(fiBmp);
        Mat img=Mat::zeros(height, width, CV_8UC3);

        uchar* p;
        for (int i = 0; i < height; i++)
        {
            p = img.ptr<uchar>(i);
            for (int j = 0; j < width; j++)
            {
                FreeImage_GetPixelIndex(fiBmp, j, i, pIntensity);

                p[3 * j] = pixels[intensity].rgbBlue;
                p[3 * j + 1] = pixels[intensity].rgbGreen;
                p[3 * j + 2] = pixels[intensity].rgbRed;
            }
        }

        return img;
    }

具体的将byte像素转化为mat里面的像素值即可，注意rgb图像的Mat里是一个像素包含三通道的值，知道这点，代码就很好理解了。

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