利用颜色范围过滤
标注与测量

代码

    #include "../common/common.hpp"

    static Rect roi;
    static void processFrame(Mat &binary, Rect &rect);

    void main(int argc, char* argv) 
    {
        VideoCapture capture;
        capture.open(getCVImagesPath("videos/video_006.mp4"));
        if (!capture.isOpened()) cout << "video not open.." << endl;

        Mat frame, mask;
        Mat kernel1 = getStructuringElement(MORPH_RECT, Size(3, 3), Point(-1, -1));
        Mat kernel2 = getStructuringElement(MORPH_RECT, Size(5, 5), Point(-1, -1));
        while (capture.read(frame)) 
        {
            inRange(frame, Scalar(0, 127, 0), Scalar(120, 255, 120), mask); // 过滤，图像二值化
            morphologyEx(mask, mask, MORPH_OPEN, kernel1, Point(-1, -1), 1); // 开操作，去椒盐噪声
            dilate(mask, mask, kernel2, Point(-1, -1), 4);// 膨胀，为后续的发现最大外接轮廓做预处理
            imshow("track mask", mask);

            processFrame(mask, roi); // 轮廓发现与在frame上位置标定
            rectangle(frame, roi, Scalar(0, 0, 255), 3, 8, 0); // 绘制位置标定
            imshow("src6-6", frame);

            if (waitKey(100) == 27) break;
        }
        capture.release();

        waitKey(0);
    }

    void processFrame(Mat &binary, Rect &rect) 
    {
        vector<vector<Point>> contours;
        vector<Vec4i> hireachy;
        findContours(binary, contours, hireachy, RETR_EXTERNAL, CHAIN_APPROX_SIMPLE, Point(0, 0));
        if (contours.size() > 0) 
        {
            double maxArea = 0.0;
            for (size_t t = 0; t < contours.size(); t++) 
            {
                double area = contourArea(contours[static_cast<int>(t)]); // 迭代找到最大外接矩形
                if (area > maxArea) 
                {
                    maxArea = area;
                    rect = boundingRect(contours[static_cast<int>(t)]);
                }
            }
        }
        else 
        {
            rect.x = rect.y = rect.width = rect.height = 0;
        }
    }

效果图