Question

I am using OpenCV in C++. I have a matrix that stores the ROI from a certain image. Now I want to calculate the mean R,G and B values of all the pixels (ROI Matrix values basically). The longer way is to use two for loops and access each pixel and then each stream. But there is a function in Open CV
Scalar mean(const Mat& mtx)
Can I use that? If yes then what would my Scalar element exactly have. The documentation states it is a 4 element vector. Which elements would contain the mean R, G and B if any?

cv::Mat3b roiMat = imgMat(cv::Rect(hSt,vSt,hEn,vEn));
mean =  cv::mean(roiMat);

What would mean have/be?

Answer 1

What about that:

cv::Mat3b roiMat = imgMat(cv::Rect(hSt,vSt,hEn,vEn));
cv::Scalar mean;
mean =  cv::mean(roiMat);
std::cout<<mean[0]<<std::endl; //blue mean
std::cout<<mean[1]<<std::endl; //green
std::cout<<mean[2]<<std::endl; //red

I hope it helps,
Good luck