在 opencv 中显示多个 windows

Question

使用以下函数，我试图绘制 3 通道照片的计算直方图，但是当我多次使用该函数时，它只显示上次调用它时的 windows不显示以前的。我如何更改它以显示所有 windows?

        void showHistogram(std::vector<cv::Mat>& hists, vector<string> titles)
    {
    // Min/Max computation
    double hmax[3] = { 0,0,0 };
    double min;
    cv::minMaxLoc(hists[0], &min, &hmax[0]);
    cv::minMaxLoc(hists[1], &min, &hmax[1]);
    cv::minMaxLoc(hists[2], &min, &hmax[2]);

    std::string wname[3] = { "blue", "green", "red" };
    cv::Scalar colors[3] = { cv::Scalar(255,0,0), cv::Scalar(0,255,0),
                             cv::Scalar(0,0,255) };

    std::vector<cv::Mat> canvas(hists.size());

    // Display each histogram in a canvas
    for (int i = 0, end = hists.size(); i < end; i++)
    {
        canvas[i] = cv::Mat::ones(125, hists[0].rows, CV_8UC3);

        for (int j = 0, rows = canvas[i].rows; j < hists[0].rows - 1; j++)
        {
            cv::line(
                canvas[i],
                cv::Point(j, rows),
                cv::Point(j, rows - (hists[i].at<float>(j) * rows / hmax[i])),
                hists.size() == 1 ? cv::Scalar(200, 200, 200) : colors[i],
                1, 8, 0
            );
        }
        if (hists.size() == 3) {
            namedWindow(titles[i]);
        cv::imshow(titles[i], canvas[i]);
        }
        else {
            cv::imshow(hists.size() == 1 ? "value" : wname[i], canvas[i]);

        }
    }
}

Answer 1

当使用相同的 window 名称时，只显示最后一张图片，因此您应该在 window 名称中添加一个唯一的东西，以防止它们相同。

例如：

#include <sstream>

        void showHistogram(std::vector<cv::Mat>& hists, vector<string> titles)
    {
    static int windowId = 0;
    std::stringstream ss;
    ss << (windowId++); // generate an unique ID for each call
    // Min/Max computation
    double hmax[3] = { 0,0,0 };
    double min;
    cv::minMaxLoc(hists[0], &min, &hmax[0]);
    cv::minMaxLoc(hists[1], &min, &hmax[1]);
    cv::minMaxLoc(hists[2], &min, &hmax[2]);

    std::string wname[3] = { "blue", "green", "red" };
    cv::Scalar colors[3] = { cv::Scalar(255,0,0), cv::Scalar(0,255,0),
                             cv::Scalar(0,0,255) };

    std::vector<cv::Mat> canvas(hists.size());

    // Display each histogram in a canvas
    for (int i = 0, end = hists.size(); i < end; i++)
    {
        canvas[i] = cv::Mat::ones(125, hists[0].rows, CV_8UC3);

        for (int j = 0, rows = canvas[i].rows; j < hists[0].rows - 1; j++)
        {
            cv::line(
                canvas[i],
                cv::Point(j, rows),
                cv::Point(j, rows - (hists[i].at<float>(j) * rows / hmax[i])),
                hists.size() == 1 ? cv::Scalar(200, 200, 200) : colors[i],
                1, 8, 0
            );
        }
        // add the ID to make the window titles unique
        if (hists.size() == 3) {
            namedWindow(titles[i] + ss.str());
        cv::imshow(titles[i] + ss.str(), canvas[i]);
        }
        else {
            cv::imshow((hists.size() == 1 ? "value" : wname[i]) + ss.str(), canvas[i]);

        }
    }
}

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