图像轮廓

1 Mat src = imread("E:/guida.png", -1);
2     Mat edge;
3     Mat dst = Mat::zeros(src.size(), src.type());
4     Canny(src, edge, 3, 9, 3);

1 vector<vector<Point>>contours;
2     vector<Vec4i>hierarchy;
3     findContours(edge, contours, hierarchy, RETR_EXTERNAL, CHAIN_APPROX_SIMPLE);
4     drawContours(dst, contours, -1, Scalar(255)); 

1     //画凸包，需要点集
2     vector<vector<Point>>hull(contours.size());
3     for (int i = 0; i < contours.size(); i++) {
4         convexHull(Mat(contours[i]), hull[i]);
5     }
6     for (int i = 0; i < contours.size(); i++) {
7         drawContours(dst, contours, i, Scalar(255));
8         drawContours(dst, hull, i, Scalar(255));
9     }

1     Rect rect = boundingRect(contours[0]);
2     rectangle(edge, rect, Scalar(255));

1     //最小包围矩形
2     RotatedRect box = minAreaRect(contours[0]);
3     Point2f vertex[4];
4     box.points(vertex);
5     for (int i = 0; i < 4; i++) {
6         line(edge, vertex[i], vertex[(i + 1)% 4], Scalar(255));
7     }

 1     //最小包围圆
 2     Point2f center;
 3     float radius;
 4     minEnclosingCircle(contours[0], center, radius);
 5     circle(edge, center, radius, Scalar(255));
 6 　　//最小包围三角形
 7     vector<Point2f> triangle;
 8     minEnclosingTriangle(contours[1], triangle);
 9     for (int i = 0; i < 3; i++)
10     line(edge, triangle[i], triangle[(i + 1) % 3], Scalar(255, 255, 0), 1, LINE_AA);

 1     vector<Point>contour;
 2     contour.push_back(Point2f(0,0));
 3     contour.push_back(Point2f(10, 0));
 4     contour.push_back(Point2f(10, 10));
 5     contour.push_back(Point2f(5, 4));
 6     double area0 = contourArea(contour);
 7     vector<Point>approx;
 8     approxPolyDP(contour, approx, 5, true);
 9     
10     double area1 = contourArea(approx);
11     Mat test = Mat::zeros(Size(50, 50), CV_8UC1);
12     Mat test1 = Mat::zeros(Size(50, 50), CV_8UC1);
13     for (int i = 0; i < contour.size(); i++)
14     {
15         line(test, contour[i], contour[(i + 1) % 4], Scalar(255));
16     }
17     for (int i = 0; i < approx.size(); i++)
18     {
19         line(test1, approx[i], approx[(i + 1) % approx.size()], Scalar(255));
20     }
　　　　double length=arcLength(approx,true);