OpenCV (C++) 几何形状识别（面积过滤、横纵比过滤等等）

转自：https://www.cnblogs.com/long5683/p/9694983.html

 1 #include <opencv2/opencv.hpp>
 2 #include <iostream>
 3 #include <math.h>
 4 
 5 using namespace cv;
 6 using namespace std;
 7 
 8 
 9 int main(int argc, char** argv)
10 {
11     Mat src = imread("3 input.bmp", IMREAD_GRAYSCALE);
12     Mat binary, dst = Mat::zeros(src.size(), CV_8UC3);
13     Mat Triangle = dst.clone(), Rect1 = dst.clone(), BigCircle = dst.clone(), SmallCircle = dst.clone();
14 
15     if (src.empty()) {
16         printf("Could not load image...");
17         return -1;
18     }
19     src = ~src;//取反
20     imshow("原图", src);
21     //二值化
22     threshold(src, binary, 0, 255, THRESH_BINARY | THRESH_OTSU);
23 
24     //发现轮廓
25     vector<vector<Point>> contours;
26     vector<Vec4i> hireachy;
27     findContours(binary, contours, hireachy, RETR_TREE, CHAIN_APPROX_SIMPLE, Point());
28 
29     //面积删选
30     for (size_t t = 0; t < contours.size(); t++)
31     {
32         double area = contourArea(contours[t]);
33         if (area < 40000) continue;//将面积小于40000的去掉
34         drawContours(Triangle, contours, t, Scalar(0, 0, 255), 2, 8, Mat(), 0, Point());
35     }
36 
37     for (size_t t = 0; t < contours.size(); t++)
38     {
39         double area = contourArea(contours[t]);
40         if (area > 40000 || area<20000) continue;//将面积小于40000的去掉
41         drawContours(BigCircle, contours, t, Scalar(0, 0, 255), 2, 8, Mat(), 0, Point());
42     }
43 
44     for (size_t t = 0; t < contours.size(); t++)
45     {
46         double area = contourArea(contours[t]);
47         if (area > 20000 || area<15000) continue;//将面积小于40000的去掉
48         drawContours(Rect, contours, t, Scalar(0, 0, 255), 2, 8, Mat(), 0, Point());
49     }
50 
51     for (size_t t = 0; t < contours.size(); t++)
52     {
53         double area = contourArea(contours[t]);
54         if (area > 15000) continue;//将面积小于40000的去掉
55         //其他过滤方法
56 
57         /*//横纵比过滤
58         Rect rect= boundingRect(contours[t]);//返回最小外接矩形
59         float ratio = float(rect.width) / float(rect.height);//计算横纵比
60         if (ratio<1.1&&ratio>0.9) {}
61         
62         //周长过滤
63         float length = arcLength(contours[t], true);//计算轮廓长度
64         
65         */
66 
67         
68         drawContours(SmallCircle, contours, t, Scalar(0, 0, 255), 2, 8, Mat(), 0, Point());
69     }
70     imshow("Triangle", Triangle);
71     imshow("BigCircle", BigCircle);
72     imshow("Rect", Rect1);
73     imshow("SmallCircle", SmallCircle);
74 
75     waitKey(0);
76     return 0;
77 }

 方法二：多边形逼近：

void approxPolyDP(InputArray curve, OutputArray approxCurve, double epsilon, bool closed)；

参数说明：

InputArray curve：输入的点集
OutputArray approxCurve：输出的点集，当前点集是能最小包容指定点集的。draw出来即是一个多边形；
double epsilon：指定的精度，也即是原始曲线与近似曲线之间的最大距离。
bool closed：若为true,则说明近似曲线是闭合的，它的首位都是相连，反之，若为false，则断开。

 

 1 #include <opencv2/opencv.hpp>
 2 #include <iostream>
 3 
 4 #define MATCHMETHOD TM_SQDIFF_NORMED//宏定义匹配模式
 5 using namespace cv;
 6 using namespace std;
 7 
 8 
 9 int main(int argc, char** argv)
10 { 
11     Mat src = imread("F:/2019视觉培训内容/2019视觉培训内容/3 input.bmp");
12     Mat src_gray,binary ;
13     Mat Triangle = src.clone(), Rect = src.clone(), BigCircle = src.clone(), SmallCircle = src.clone();
14     if (src.empty()) {
15         printf("Could not load image...");
16         return -1;
17     }
18     imshow("Input Image",src);
19       
20     //二值化
21     cvtColor(src, src_gray, COLOR_BGR2GRAY);
22     threshold(src_gray, binary, 0, 255, THRESH_BINARY | THRESH_OTSU);
23     binary = ~binary;
24     imshow("binary", binary);
25 
26     //发现轮廓
27     vector<vector<Point>> contours;
28     vector<Point> point;
29     vector<Vec4i> hireachy;
30     findContours(binary, contours, hireachy, RETR_TREE, CHAIN_APPROX_SIMPLE, Point());
31     
32     //绘制出所有轮廓
33     for (size_t t = 0; t < contours.size(); t++)
34     {
35                 
36         int epsilon = 0.01*arcLength(contours[t], true);
37         approxPolyDP(contours[t], point, epsilon, true);
38         if(point.size()==3)
39         {
40             drawContours(Triangle, contours, t, Scalar(0, 0, 255), 2, 8, Mat(), 0, Point());//dst必须先初始化 
41         }
42         else if (point.size() == 4)
43         {
44             drawContours(Rect, contours, t, Scalar(0, 0, 255), 2, 8, Mat(), 0, Point());//dst必须先初始化
45         }
46 
47         else 
48         {
49             double area = contourArea(contours[t]);
50             if (area < 15000)
51             {
52                 drawContours(SmallCircle, contours, t, Scalar(0, 0, 255), 2, 8, Mat(), 0, Point());//dst必须先初始化
53             }
54             else
55             {
56                 drawContours(BigCircle, contours, t, Scalar(0, 0, 255), 2, 8, Mat(), 0, Point());//dst必须先初始化
57             }
58         }
59         
60         cout << "边的数目：" << point.size() << endl;
61     }
62 
63     imshow("Triangle", Triangle);
64     imshow("BigCircle", BigCircle);
65     imshow("Rect", Rect);
66     imshow("SmallCircle", SmallCircle);
67 
68     waitKey(0);
69 
70     return 0;
71 }