通过C++ wrapper实现访问图像像素

template<class T> class Image
 {
     private:
         IlpImage *imgp;
     public:
         Image(IplImage* img = 0)
         {
             imgp = img;
         }
         inline T* operator[](const int rowIndx)
         {
             return( (T*)(imgp ->imageData + rowIndx * imgp ->widthStep));
         }
 };
 
 typedef struct {
     unsigned char b, g, r;
 }RgbPixel;
 
 typedef struct {
     float b, g, r;
 }RgbPixelFloat;
 
 typedef Image<RgbPixel>      RgbImage;
 typedef Imgae<RgbPixelFloat> RgbImageFloat;
 typedef Image<unsigned char> BwImage;
 typedef Image<float>         BwImageFloat;

例：对3通道的字节型图像访问如下：
 IplImage* img = cvCreateImage(cvSize(640, 480), IPL_DEPTH_8U, 3);
 RgbImage imgA(img);
 //假设访问第K通道、第i行、第j列的像素
 imgA[i][j].b = 111;
 imgA[i][j].g = 111;
 imgA[i][j].r = 111;