OpenCV示例学习笔记（1）-contours2.cpp-通过findContours 函数实现轮廓提取

 1 #include "opencv2/imgproc/imgproc.hpp"
 2 #include "opencv2/highgui/highgui.hpp"
 3 #include <math.h>
 4 #include <iostream>
 5 
 6 using namespace cv;
 7 using namespace std;
 8 
 9 static void help()
10 {
11     cout
12     << "\nThis program illustrates the use of findContours and drawContours\n"
13     << "The original image is put up along with the image of drawn contours\n"
14     << "Usage:\n"
15     << "./contours2\n"
16     << "\nA trackbar is put up which controls the contour level from -3 to 3\n"
17     << endl;
18 }
19 
20 const int w = 500;
21 int levels = 3;
22 
23 vector<vector<Point> > contours;
24 vector<Vec4i> hierarchy;
25 
26 static void on_trackbar(int, void*)
27 {
28     Mat cnt_img = Mat::zeros(w, w, CV_8UC3);
29     int _levels = levels - 3;
30     drawContours( cnt_img, contours, _levels <= 0 ? 3 : -1, Scalar(128,255,255),
31                   3, LINE_AA, hierarchy, std::abs(_levels) );
32 
33     imshow("contours", cnt_img);
34 }
35 
36 int main( int argc, char**)
37 {
38     Mat img = Mat::zeros(w, w, CV_8UC1);
39     if(argc > 1)
40     {
41         help();
42         return -1;
43     }
44     //Draw 6 faces
45     for( int i = 0; i < 6; i++ )
46     {
47         int dx = (i%2)*250 - 30;
48         int dy = (i/2)*150;
49         const Scalar white = Scalar(255);
50         const Scalar black = Scalar(0);
51 
52         if( i == 0 )
53         {
54             for( int j = 0; j <= 10; j++ )
55             {
56                 double angle = (j+5)*CV_PI/21;
57                 line(img, Point(cvRound(dx+100+j*10-80*cos(angle)),
58                     cvRound(dy+100-90*sin(angle))),
59                     Point(cvRound(dx+100+j*10-30*cos(angle)),
60                     cvRound(dy+100-30*sin(angle))), white, 1, 8, 0);
61             }
62         }
63 
64         ellipse( img, Point(dx+150, dy+100), Size(100,70), 0, 0, 360, white, -1, 8, 0 );
65         ellipse( img, Point(dx+115, dy+70), Size(30,20), 0, 0, 360, black, -1, 8, 0 );
66         ellipse( img, Point(dx+185, dy+70), Size(30,20), 0, 0, 360, black, -1, 8, 0 );
67         ellipse( img, Point(dx+115, dy+70), Size(15,15), 0, 0, 360, white, -1, 8, 0 );
68         ellipse( img, Point(dx+185, dy+70), Size(15,15), 0, 0, 360, white, -1, 8, 0 );
69         ellipse( img, Point(dx+115, dy+70), Size(5,5), 0, 0, 360, black, -1, 8, 0 );
70         ellipse( img, Point(dx+185, dy+70), Size(5,5), 0, 0, 360, black, -1, 8, 0 );
71         ellipse( img, Point(dx+150, dy+100), Size(10,5), 0, 0, 360, black, -1, 8, 0 );
72         ellipse( img, Point(dx+150, dy+150), Size(40,10), 0, 0, 360, black, -1, 8, 0 );
73         ellipse( img, Point(dx+27, dy+100), Size(20,35), 0, 0, 360, white, -1, 8, 0 );
74         ellipse( img, Point(dx+273, dy+100), Size(20,35), 0, 0, 360, white, -1, 8, 0 );
75     }
76     //show the faces
77     namedWindow( "image", 1 );
78     imshow( "image", img );
79     //Extract the contours so that
80     vector<vector<Point> > contours0;
81     findContours( img, contours0, hierarchy, RETR_TREE, CHAIN_APPROX_SIMPLE);
82 
83     contours.resize(contours0.size());
84     for( size_t k = 0; k < contours0.size(); k++ )
85         approxPolyDP(Mat(contours0[k]), contours[k], 3, true);
86 
87     namedWindow( "contours", 1 );
88     createTrackbar( "levels+3", "contours", &levels, 7, on_trackbar );
89 
90     on_trackbar(0,0);
91     waitKey();
92 
93     return 0;
94 }