opencv学习之路（24）、轮廓查找与绘制（三）——凸包

一、简介

二、绘制点集的凸包

 #include<opencv2/opencv.hpp>
 using namespace cv;

 void main()
 {
     //---绘制点集的凸包
     Mat img(, , CV_8UC3, Scalar::all());  //定义绘制图像
     RNG rng;  //定义随机数对象
     while()
     {
         char key;
         int count = (unsigned int)rng % ;  //定义点的个数
         vector<Point> points;  //定义点集
         for(int i=; i<count; i++)
         {
             Point pt;
             pt.x = rng.uniform(img.cols/, img.cols*/);  //设定点的x范围
             pt.y = rng.uniform(img.rows/, img.rows*/);  //设定点的y范围
             points.push_back(pt);
         }

         //检测凸包
         vector<int> hull;
         convexHull(Mat(points), hull, true);

         img = Scalar::all();
         for(int i = ; i < count; i++ )
             circle(img, points[i], , Scalar(rng.uniform(, ), rng.uniform(, ), rng.uniform(, )), CV_FILLED, CV_AA);

         //准备参数
         int hullcount = (int)hull.size(); //凸包的边数
         Point point0 = points[hull[hullcount-]]; //连接凸包边的坐标点

         //绘制凸包的边
         for(int  i = ; i < hullcount; i++ )
         {
             Point point = points[hull[i]];
             circle(img, point, , Scalar(, , ), , );
             line(img, point0, point, Scalar(, , ), , CV_AA);
             point0 = point;
         }

         //显示效果图
         imshow("img", img);

         //按下ESC,Q,或者q，程序退出
         key = (char)waitKey();
         if( key ==  || key == 'q' || key == 'Q' )
             break;
     }
}

三、绘制轮廓的凸包

 #include<opencv2/opencv.hpp>
 using namespace cv;

 void main()
 {
     Mat srcImg = imread("E://12.jpg");
     imshow("src", srcImg);
     Mat dstImg2 = srcImg.clone();
     Mat tempImg(srcImg.rows, srcImg.cols, CV_8UC3, Scalar::all());  //用于绘制凸包
     Mat dstImg(srcImg.rows, srcImg.cols, CV_8UC3, Scalar::all());  //用于绘制轮廓
     cvtColor(srcImg, srcImg, CV_BGR2GRAY);
     threshold(srcImg, srcImg, , , CV_THRESH_BINARY); //二值化

     vector<vector<Point>> contours;
     vector<Vec4i> hierarcy;
     findContours(srcImg, contours, hierarcy, CV_RETR_EXTERNAL, CV_CHAIN_APPROX_NONE);
     vector<vector<Point>> hull(contours.size());
     for(int i=; i<contours.size(); i++)
     {
         convexHull(Mat(contours[i]), hull[i], true);     //查找凸包
         drawContours(dstImg, contours, i, Scalar(, , ), -, );  //绘制轮廓
         //drawContours(dstImg, hull, i, Scalar(rand()%255, rand()%255, rand()%255), 2, 8);
         drawContours(tempImg, hull, i, Scalar(, , ), -, );
     }
     imshow("hull", tempImg);
     imshow("contours", dstImg);

     Mat diffImg;
     absdiff(tempImg, dstImg, diffImg);  //图像相减
     Mat element = getStructuringElement(MORPH_RECT, Size(, ), Point(-, -));
     erode(diffImg, diffImg, element);
     imshow("diff", diffImg);

     vector<vector<Point>> contours2;
     vector<Vec4i> hierarcy2;
     cvtColor(diffImg, diffImg, CV_BGR2GRAY); //转为灰度图
     threshold(diffImg, diffImg, , , CV_THRESH_BINARY); //二值化
     findContours(diffImg, contours2, hierarcy2, CV_RETR_EXTERNAL, CV_CHAIN_APPROX_NONE);
     drawContours(dstImg2, contours2, -, Scalar(, , ), , );  //红色绘制缺陷轮廓
     imshow("defects", dstImg2);
     waitKey();
 }