Creating mask move over image and count pixel number every time it move

simple code that loop binary mask over image, as in conv2 function. Every time the mask move, it should count the pixel, if it is not on the pixel range ignore it, if it is take it The basic idea is to integrate conv2 source code with pixel counter code, or edit conv2 source code to make the mask count the pixel every time it move and ignore region out of the pixel range, the conv2 source code and pixel counter code are attached,also I attached image to illustrate the result