opencv（NoneAPI100例---2）--灰度化

灰度是一种图像亮度的表示方法，通过下式计算： $$ Y = 0.2126\ R + 0.7152\ G + 0.0722\ B $$

Mat BGR2GRY(Mat img)

{

        int width = img.cols;

        int height = img.rows;

        Mat out = Mat::zeros(height,width,CV_8UC1);

        for (int h = 0; h < height; h++)

         {

                for (int w = 0; w < width; w++)

                {

                        out.at<uchar>(h, w) = 0.2126 * (float)img.at<cv::Vec3b>(h, w)[2] \

                            + 0.7152 * (float)img.at<cv::Vec3b>(h, w)[1] \

                            + 0.0722 * (float)img.at<cv::Vec3b>(h, w)[0];

                }

        }

        return out;

}

Mat img = cv::imread("D:/chat.png", cv::IMREAD_COLOR);

Mat out = BGR2GRY(img);

imshow("old", img);

imshow("new", out);