OpenCV凸包
一、概述
案例:输入一张图片将其凸包绘制出来
概念:最大外接多边形
convexHull( InputArray points,// 输入候选点,来自findContours OutputArray hull,// 凸包 bool clockwise,// default true, 顺时针方向 bool returnPoints)// true 表示返回点个数,如果第二个参数是 vector<Point>则自动忽略 )
ps:凸包检测是基于轮廓发现候选点的
实现步骤:
1.加载图像,并将图像转为灰度图
2.执行边缘检测
3.发现轮廓
4.在轮廓中检测凸包
5.绘制凸包和轮廓
6.显示凸包和轮廓
二、代码示例
Mat src = imread(filePath); if(src.empty()){ return; } imshow("src",src); Mat gray; cvtColor(src,gray,COLOR_BGR2GRAY); imshow("gray",gray); //执行边缘 检测 Canny(gray,gray,50,100,3,false); imshow("canny",gray); //发现轮廓 vector<vector<Point>> contours; vector<Vec4i> hierarchy; findContours(gray,contours,hierarchy,RETR_TREE,CHAIN_APPROX_SIMPLE,Point(0,0)); //绘制轮廓 RNG rng; Mat drawImg=Mat::zeros(gray.size(),CV_8UC3); //从轮廓数据中检测凸包 vector<vector<Point>> hull(contours); for(int i=0;i<contours.size();i++){ convexHull(Mat(contours[i]),hull[i],false); } for(int i=0;i<contours.size();i++){ double area = contourArea(contours[i],false); if(area>100){ Scalar color = Scalar(rng.uniform(0,255),rng.uniform(0,255),rng.uniform(0,255)); //绘制凸包 drawContours(drawImg,hull,i,color,1,LINE_8,hierarchy,0,Point(0,0)); //绘制轮廓 drawContours(drawImg,contours,i,color,2,LINE_8,hierarchy,0,Point(0,0)); } } imshow("drawImg",drawImg);
三、是图片