chore: import upstream snapshot with attribution

samples/cpp/segment_objects.cpp

@@ -0,0 +1,119 @@
+#include "opencv2/imgproc.hpp"
+#include "opencv2/videoio.hpp"
+#include "opencv2/highgui.hpp"
+#include "opencv2/video/background_segm.hpp"
+#include <stdio.h>
+#include <string>
+
+using namespace std;
+using namespace cv;
+
+static void help(char** argv)
+{
+    printf("\n"
+            "This program demonstrated a simple method of connected components clean up of background subtraction\n"
+            "When the program starts, it begins learning the background.\n"
+            "You can toggle background learning on and off by hitting the space bar.\n"
+            "Call\n"
+            "%s [video file, else it reads camera 0]\n\n", argv[0]);
+}
+
+static void refineSegments(const Mat& img, Mat& mask, Mat& dst)
+{
+    int niters = 3;
+
+    vector<vector<Point> > contours;
+    vector<Vec4i> hierarchy;
+
+    Mat temp;
+
+    dilate(mask, temp, Mat(), Point(-1,-1), niters);
+    erode(temp, temp, Mat(), Point(-1,-1), niters*2);
+    dilate(temp, temp, Mat(), Point(-1,-1), niters);
+
+    findContours( temp, contours, hierarchy, RETR_CCOMP, CHAIN_APPROX_SIMPLE );
+
+    dst = Mat::zeros(img.size(), CV_8UC3);
+
+    if( contours.size() == 0 )
+        return;
+
+    // iterate through all the top-level contours,
+    // draw each connected component with its own random color
+    int idx = 0, largestComp = 0;
+    double maxArea = 0;
+
+    for( ; idx >= 0; idx = hierarchy[idx][0] )
+    {
+        const vector<Point>& c = contours[idx];
+        double area = fabs(contourArea(Mat(c)));
+        if( area > maxArea )
+        {
+            maxArea = area;
+            largestComp = idx;
+        }
+    }
+    Scalar color( 0, 0, 255 );
+    drawContours( dst, contours, largestComp, color, FILLED, LINE_8, hierarchy );
+}
+
+
+int main(int argc, char** argv)
+{
+    VideoCapture cap;
+    bool update_bg_model = true;
+
+    CommandLineParser parser(argc, argv, "{help h||}{@input||}");
+    if (parser.has("help"))
+    {
+        help(argv);
+        return 0;
+    }
+    string input = parser.get<std::string>("@input");
+    if (input.empty())
+        cap.open(0);
+    else
+        cap.open(samples::findFileOrKeep(input));
+
+    if( !cap.isOpened() )
+    {
+        printf("\nCan not open camera or video file\n");
+        return -1;
+    }
+
+    Mat tmp_frame, bgmask, out_frame;
+
+    cap >> tmp_frame;
+    if(tmp_frame.empty())
+    {
+        printf("can not read data from the video source\n");
+        return -1;
+    }
+
+    namedWindow("video", 1);
+    namedWindow("segmented", 1);
+
+    Ptr<BackgroundSubtractorMOG2> bgsubtractor=createBackgroundSubtractorMOG2();
+    bgsubtractor->setVarThreshold(10);
+
+    for(;;)
+    {
+        cap >> tmp_frame;
+        if( tmp_frame.empty() )
+            break;
+        bgsubtractor->apply(tmp_frame, bgmask, update_bg_model ? -1 : 0);
+        refineSegments(tmp_frame, bgmask, out_frame);
+        imshow("video", tmp_frame);
+        imshow("segmented", out_frame);
+        char keycode = (char)waitKey(30);
+        if( keycode == 27 )
+            break;
+        if( keycode == ' ' )
+        {
+            update_bg_model = !update_bg_model;
+            printf("Learn background is in state = %d\n",update_bg_model);
+        }
+    }
+
+    return 0;
+}