OpenCV - imagedata的加減

IplImage *img = cvCreateImage(cvSize(5,3), 8, 1);

img->imageData[1*img->widthStep] = 178;
img->imageData[1*img->widthStep+1] = 177;

img->imageData[1*img->widthStep]+=img->imageData[1*img->widthStep+1];
cout << "img[1,0] = " << (double)(uchar)img->imageData[1*img->widthStep];

經過上面程式碼後，會print:
99