Mat src=imread("abc.jpg");
if(!src.data)
return -1;
Mat dst;
cvtColor(src, dst, CV_RGB2GRAY);//[s:274]
namedWindow("rgb2gray", CV_WINDOW_AUTOSIZE);
imshow("rgb2gray", dst);
waitKey();
if(!src.data)
return -1;
Mat dst;
cvtColor(src, dst, CV_RGB2GRAY);//[s:274]
namedWindow("rgb2gray", CV_WINDOW_AUTOSIZE);
imshow("rgb2gray", dst);
waitKey();