opencv/cxcore.go
func GetSubRect(arr Arr, submat *Mat, rect Rect) *Mat {
	mat_new := C.cvGetSubRect(
		unsafe.Pointer(arr),
		(*C.CvMat)(submat),
		(C.CvRect)(rect),
	)
	return (*Mat)(mat_new)
}
func GetSubRect(arr Arr, submat *Mat, rect Rect) *Mat {
	mat_new := C.cvGetSubRect(
		unsafe.Pointer(arr),
		(*C.CvMat)(submat),
		(C.CvRect)(rect),
	)
	return (*Mat)(mat_new)
}
/* Makes a new matrix from <rect> subrectangle of input array.
   No data is copied */