opencv之绘制轮廓（代码实现）

#include <opencv2/opencv.hpp>
#include <iostream>
using namespace std;
using namespace cv;
Mat src, dst, canny_src;
int threshold_value = 100;
int max_threshold = 255;
RNG rng(12345);
void demo_contours(int, void*);
int main(){
 src = imread("D:/photo/circle.jpg");
 if (src.empty())
 {
 cout << "open no success!" << endl;
 return -1;
 }
 //创建显示窗口
 namedWindow("out image", WINDOW_AUTOSIZE);
 //显示原图片
 imshow("input", src);
 //转换到灰度图单通道
 cvtColor(src, canny_src, CV_BGR2GRAY);
 //创建滑块进行阈值选择
 createTrackbar("threshole", "out image", &threshold_value, max_threshold, demo_contours);
 demo_contours(0,0);
 waitKey(0);
 return 0;
}
void demo_contours(int, void*){
 //初始化轮廓向量和序号向量，固定的
 vector<vector<Point>> contours;
 vector<Vec4i> hierachy;
 //阈值去噪声
 Canny(canny_src, canny_src, threshold_value, 2* threshold_value, 3, false);
 //寻找轮廓
 findContours(canny_src, contours, hierachy, RETR_TREE, 1);
 dst = Mat::zeros(src.size(), src.type());
 for (size_t i = 0; i < contours.size(); i++)
 {
 //绘制轮廓
 Scalar color = Scalar(rng.uniform(0,255), rng.uniform(0,255), rng.uniform(0,255));
 drawContours(dst, contours, i, color, 2, 8, hierachy, 0, Point(0,0));
 }
 imshow("out image", dst);
}