1、convexHull函数
函数的作用:
计算出图像的凸包,这里是根据图像的轮廓点,通过函数 convexHull 转化成凸包的点点的坐标,
从而画出图像的凸包。
2、 convexHull函数的调用形式
C++: void convexHull(InputArray points, OutputArray hull, bool clockwise=false, bool returnPoints=true )
参数详解:
InputArray points:得到的点集,一般是用图像轮廓函数求得的轮廓点
OutputArray hull:输出的是凸包的二维xy点的坐标值,针对每一个轮廓形成的
bool clockwise=false:表示凸包的方向,顺时针或者逆时针
bool returnPoints=true:表示返回点还是点地址的索引,
3、opencv代码
#include "opencv2/highgui/highgui.hpp" #include "opencv2/imgproc/imgproc.hpp" #include <iostream> #include <stdio.h> #include <stdlib.h> using namespace cv; using namespace std; Mat src; Mat src_gray; int thresh = 100; int max_thresh = 255; RNG rng(12345); /// Function header void thresh_callback(int, void* ); /** @function main */ int main( int argc, char** argv ) { /// 加载源图像 src = imread( argv[1], 1 ); /// 转成灰度图并进行模糊降噪 cvtColor( src, src_gray, CV_BGR2GRAY ); blur( src_gray, src_gray, Size(3,3) ); /// 创建窗体 char* source_window = "Source"; namedWindow( source_window, CV_WINDOW_AUTOSIZE ); imshow( source_window, src ); createTrackbar( " Threshold:", "Source", &thresh, max_thresh, thresh_callback ); thresh_callback( 0, 0 ); waitKey(0); return(0); } /** @function thresh_callback */ void thresh_callback(int, void* ) { Mat src_copy = src.clone(); Mat threshold_output; vector<vector<Point> > contours; vector<Vec4i> hierarchy; /// 对图像进行二值化 threshold( src_gray, threshold_output, thresh, 255, THRESH_BINARY ); /// 寻找轮廓 findContours( threshold_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) ); /// 对每个轮廓计算其凸包 vector<vector<Point> >hull( contours.size() ); for( int i = 0; i < contours.size(); i++ ) { convexHull( Mat(contours[i]), hull[i], false ); } /// 绘出轮廓及其凸包 Mat drawing = Mat::zeros( threshold_output.size(), CV_8UC3 ); for( int i = 0; i< contours.size(); i++ ) { Scalar color = Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) ); drawContours( drawing, contours, i, color, 1, 8, vector<Vec4i>(), 0, Point() ); drawContours( drawing, hull, i, color, 1, 8, vector<Vec4i>(), 0, Point() ); } /// 把结果显示在窗体 namedWindow( "Hull demo", CV_WINDOW_AUTOSIZE ); imshow( "Hull demo", drawing ); }