opencv_19_图像直方图

1)void histogram_demo(Mat& image);

2)void ColorInvert::histogram_demo(Mat& image) {
    std::vector<Mat>bgr_plane;
    split(image, bgr_plane);
    const int channels[1] = { 0 };
    const int bins[1] = { 256 };
    float hranges[2] = { 0,255 };
    const float* ranges[1] = { hranges };

    Mat b_hist;
    Mat g_hist;
    Mat r_hist;

    calcHist(&bgr_plane[0], 1, 0, Mat(), b_hist, 1, bins, ranges);
    calcHist(&bgr_plane[1], 1, 0, Mat(), g_hist, 1, bins, ranges);
    calcHist(&bgr_plane[2], 1, 0, Mat(), r_hist, 1, bins, ranges);

    int hist_w = 512;
    int hist_h = 400;
    int bin_w = cvRound((double)hist_w / bins[0]);

    Mat histImage = Mat::zeros(hist_h, hist_w, CV_8UC3);

    normalize(b_hist, b_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat());
    normalize(g_hist, g_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat());
    normalize(r_hist, r_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat());

    for (int i = 1; i < bins[0]; i++)
    {
        line(histImage, Point(bin_w * (i - 1), hist_h - cvRound(b_hist.at<float>(i - 1))), Point(bin_w * (i),hist_h-cvRound(b_hist.at<float>(i))),Scalar(255,0,0),2,8,0);
        line(histImage, Point(bin_w * (i - 1), hist_h - cvRound(b_hist.at<float>(i - 1))), Point(bin_w * (i), hist_h - cvRound(b_hist.at<float>(i))), Scalar(255, 0, 0), 2, 8, 0);
        line(histImage, Point(bin_w * (i - 1), hist_h - cvRound(b_hist.at<float>(i - 1))), Point(bin_w * (i), hist_h - cvRound(b_hist.at<float>(i))), Scalar(255, 0, 0), 2, 8, 0);
    }
    namedWindow("Histogram Demo", WINDOW_AUTOSIZE);
    imshow("Histogram Demo", histImage);
}

直方图：