create()
is a member function of cv::Mat
class.
void Mat::create(int rows, int cols, int type)
It is used to create a cv::Mat
and allocates new array data if needed.
In your example, grey
will be a sizes[0] x sizes[1]
matrix, i.e. Mat
image with type CV_8U
. grey
can be viewed as a gray-scale image here with only one-channel, which is equivalent to:
Mat grey(sizes[0], sizes[1], CV_8UC1);