image.at<DATA_TYPE>(ROW, COL)

• 1 channel 일 떄
  • image_grey.at<uchar>(50,100);
• BGR
  • image.at<Vec3b>(50,100)[i];

ptr - at 보다 빠름

channels = image.channels();
uchar* p = image.ptr<uchar>(50);
b = p[100*channels + 0];
g = p[100*channels + 1];
r = p[100*channels + 2];

data - 빠름

uchar* data = (uchar*)image.data;
b = data[(50*image.cols + 100) *channels + 0];
g = data[(50*image.cols + 100) *channels + 1];
r = data[(50*image.cols + 100) *channels + 2];