I have a code written using OpenCV in C++, and this code uses a function setTo. Basically, it is used as:
cv::Mat xx; //prefedined and has some values cv::Ma
yy.setTo(0) will set all the pixels to 0.
yy.setTo(0)
yy.setTo(0, xx) will set all the pixels who have a corresponding pixel with a non-zero value in the xx Mat to 0.
yy.setTo(0, xx)
Mat
Example:
yy = 2 2 2 2 2 2 2 2 2 xx = 0 0 0 0 1 0 0 0 0 yy.setTo(0, xx) => yy = 2 2 2 2 0 2 2 2 2