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• 繼續上一篇 OpenCV3.1 搜尋輪廓與遮罩應用

• 現在要計算輪廓周長、面積和重心，並且用一多邊形曲線近似該輪廓。

•    1:  

     2:     for (int i = 0; i < contours.size(); i++) {

     3:         cout << "contour # " << i << endl;

     4:         imgMask = Mat::zeros(imgSrc.size(), CV_8UC1);

     5:         drawContours(imgMask, contours, i, Scalar(255), -1);

     6:         Mat imgROI;

     7:         imgSrc.copyTo(imgROI, imgMask);

     8:         string name = std::to_string(i);

     9:         //imshow(name, imgROI);

    10:         cout << "mean color (BGR) = " << mean(imgSrc, imgMask) << endl;

    11:         Moments m = moments(contours[i]);

    12:         cout << "area = " << m.m00 <<endl;

    13:         double contArea = contourArea(contours[i]);

    14:         cout << "contour area = " << contArea << endl;

    15:         double cx = m.m10 / m.m00;

    16:         double cy = m.m01 / m.m00;

    17:         line(imgROI, Point(cx, cy), Point(cx, cy), Scalar(255, 0, 0), 5, 8);

    18:         char label[50];

    19:         sprintf_s(label, "(%.0f,%.0f)", cx, cy);

    20:         int offset = 100;

    21:         putText(imgROI, label, Point(cx-offset, cy), FONT_HERSHEY_COMPLEX, 1, Scalar(0, 0, 255), 1, 8);

    22:         double perimeter = arcLength(contours[i], true);

    23:         cout << "perimeter = " << perimeter << endl;

    24:         vector<Point> polyCurves;

    25:         double epsilon = 0.01;

    26:         approxPolyDP(contours[i], polyCurves, epsilon*arcLength(contours[i], true), true);

    27:         

    28:         cout << "polygonal curves = " << polyCurves.size() << endl;

    29:         for (int j = 0; j < polyCurves.size()-1; j++) 

    30:         {

    31:             Scalar color = Scalar(rng.uniform(0, 255), rng.uniform(0, 255), rng.uniform(0, 255));

    32:             line(imgROI, polyCurves[j], polyCurves[j + 1], color, 3, 8);

    33:         }

    34:  

    35:         line(imgROI, polyCurves[0], polyCurves[polyCurves.size()-1], Scalar(0, 0,255), 3, 8);

    36:             

    37:         imshow(name, imgROI);

    38:         cout << "------------------------------" << endl;

    39:     }

多邊形曲線近似 epsilon = 0.01

多邊形曲線近似 epsilon = 0.02

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輪廓極值(minX, maxX, minY, maxY)

   1:  

   2: bool sortByXAscend(Point a, Point b) { return (a.x<b.x); }

   3: bool sortByXDescend(Point a, Point b) { return (a.x>b.x); }

   4: bool sortByYAscend(Point a, Point b) { return (a.y<b.y); }

   5: bool sortByYDescend(Point a, Point b) { return (a.y>b.y); }

   1:  

   2:     sort(polyCurves.begin(), polyCurves.end(), sortByXAscend);

   3:     cout << "sortByXAsc : " << polyCurves << endl;

   4:     circle(imgROI, polyCurves[0], 10, Scalar(0, 0, 255),-1);

   5:     sort(polyCurves.begin(), polyCurves.end(), sortByXDescend);

   6:     cout << "sortByXDescend : " << polyCurves << endl;

   7:     circle(imgROI, polyCurves[0], 10, Scalar(0, 255, 0), -1);

   8:  

   9:     sort(polyCurves.begin(), polyCurves.end(), sortByYAscend);

  10:     cout << "sortByYAsc : " << polyCurves << endl;

  11:     circle(imgROI, polyCurves[0], 10, Scalar(255, 255, 0), -1);

  12:  

  13:     sort(polyCurves.begin(), polyCurves.end(), sortByYDescend);

  14:     cout << "sortByYDescend : " << polyCurves << endl;

  15:     circle(imgROI, polyCurves[0], 10, Scalar(255, 255, 255), -1);

參考資料

1. Contours - 2 : Brotherhood

2. Contours - 3 : Extraction

3. std::sort