本文转载http://blog.csdn.net/qq_18343569/article/details/47999257
1、approxPolyDP函数
函数的作用：
对图像轮廓点进行多边形拟合
2、函数的调用形式
C++: void approxPolyDP(InputArray curve, OutputArray approxCurve, double epsilon, bool closed)
参数详解;
InputArray curve:一般是由图像的轮廓点组成的点集
OutputArray approxCurve：表示输出的多边形点集
double epsilon：主要表示输出的精度，就是另个轮廓点之间最大距离数，5,6,7，，8，，,,，
bool closed：表示输出的多边形是否封闭
3、OPENCV代码
1 #include "opencv2/highgui/highgui.hpp" 2 #include "opencv2/imgproc/imgproc.hpp" 3 #include <iostream> 4 #include <stdio.h> 5 #include <stdlib.h> 6 7 using namespace cv; 8 using namespace std; 9 10 Mat src; Mat src_gray; 11 int thresh = 100; 12 int max_thresh = 255; 13 RNG rng(12345); 14 15 /// Function header 16 void thresh_callback(int, void*); 17 18 /** @function main */ 19 int main(int argc, char** argv) 20 { 21 /// 加载源图像 22 src = imread("D:6.jpg", 1); 23 24 /// 转成灰度图并进行模糊降噪 25 cvtColor(src, src_gray, CV_BGR2GRAY); 26 blur(src_gray, src_gray, Size(3, 3)); 27 28 /// 创建窗体 29 char* source_window = "Source"; 30 namedWindow(source_window, CV_WINDOW_AUTOSIZE); 31 imshow(source_window, src); 32 33 createTrackbar(" Threshold:", "Source", &thresh, max_thresh, thresh_callback); 34 thresh_callback(0, 0); 35 36 waitKey(0); 37 return(0); 38 } 39 40 /** @function thresh_callback */ 41 void thresh_callback(int, void*) 42 { 43 Mat src_copy = src.clone(); 44 Mat threshold_output; 45 vector<vector<Point> > contours; 46 vector<Vec4i> hierarchy; 47 48 /// 对图像进行二值化 49 threshold(src_gray, threshold_output, thresh, 255, THRESH_BINARY); 50 51 /// 寻找轮廓 52 findContours(threshold_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0)); 53 /*Mat drawing = Mat::zeros(threshold_output.size(), CV_8UC3);*/ 54 55 /* 对每个轮廓计算其凸包*/ 56 vector<vector<Point> >poly(contours.size()); 57 for (int i = 0; i < contours.size(); i++) 58 { 59 approxPolyDP(Mat(contours[i]), poly[i], 5,true); 60 } 61 62 /* 绘出轮廓及其凸包*/ 63 Mat drawing = Mat::zeros(threshold_output.size(), CV_8UC3); 64 for (int i = 0; i< contours.size(); i++) 65 { 66 Scalar color = Scalar(rng.uniform(0, 255), rng.uniform(0, 255), rng.uniform(0, 255)); 67 drawContours(drawing, contours, i, color, 1, 8, vector<Vec4i>(), 0, Point()); 68 drawContours(drawing, poly, i, color, 1, 8, vector<Vec4i>(), 0, Point()); 69 } 70 /*vector<Point> poly; 71 approxPolyDP(Mat(contours[3]), poly, 5, false); 72 vector<Point>::const_iterator itp = poly.begin(); 73 while (itp != (poly.end() - 2)) 74 { 75 line(drawing, *itp, *(itp + 1), Scalar(255), 2); 76 ++itp; 77 } 78 line(drawing, *itp, *(poly.begin()), Scalar(255), 2);*/ 79 /// 把结果显示在窗体 80 namedWindow("Hull demo", CV_WINDOW_AUTOSIZE); 81 imshow("Hull demo", drawing); 82 }