Add overlay with alpha channel on an image using OpenCV

bool Overlay(cv::Mat& img, cv::Mat& ovr)
	if (img.cols != ovr.cols || img.rows != ovr.rows)
		return false;
#pragma omp parallel for // make sure to add #include <omp.h> and -fopenmp
	for (int i = 0; i < img.rows; i++){
		for (int j = 0; j < img.cols; j++){
			cv::Vec4b bytes =<cv::Vec4b>(i, j);
			if (bytes[3] == 255){<cv::Vec3b>(i, j)[0] =<cv::Vec4b>(i, j)[0];<cv::Vec3b>(i, j)[1] =<cv::Vec4b>(i, j)[1];<cv::Vec3b>(i, j)[2] =<cv::Vec4b>(i, j)[2];
	return true;