openCV实现图像的轮廓检测以及外接矩形

Bertha 。 2022-06-12 04:48 351阅读 0赞

前两篇博文分别介绍了图像的边缘检测和轮廓检测，本文接着介绍图像的轮廓检测和轮廓外接矩形：

一、代码部分：

// extract_contours.cpp : 定义控制台应用程序的入口点。
    //
    #include "stdafx.h"
    #include<cv.h> 
    #include<highgui.h> 
    using namespace cv;
    using namespace std;
    
    int _tmain(int argc, _TCHAR* argv[])
    {
        //load src image
        string img_name="..\\image_norm\\71253.jpg";
        Mat image=imread(img_name); 
        imshow("src_image",image);
        cvWaitKey(0);
        //convert into gray image
        Mat gray(image.size(),CV_8U);  
        cvtColor(image,gray,CV_BGR2GRAY);
        imshow("gray",gray);
        cvWaitKey(0);
        //convert into bin image
        threshold(gray,gray,128,255,THRESH_BINARY);//转换成2值图像 
        imshow("binary",gray); 
        cvWaitKey(0);
        // Detecting contours 
        vector<vector<Point>> contours;  //定义轮廓集合 
        vector<Vec4i> hierarchy; 
        findContours(gray, contours, hierarchy, CV_RETR_EXTERNAL, CV_CHAIN_APPROX_NONE);//CV_RETR_EXTERNAL只检测外部轮廓
        // draw black contours on white image 
        Mat result(gray.size(),CV_8U,Scalar(255));  
        int index = 0;  
        for (; index >= 0; index = hierarchy[index][0]) //hierarchy[index][0]表示后一个轮廓
        {  
            Scalar color(rand() & 255, rand() & 255, rand() & 255);  
            drawContours(result, contours, index, Scalar(0), 1, 8, hierarchy);//描绘字符的外轮廓 
            Rect rect = boundingRect(contours[index]);//检测外轮廓 
            rectangle(result, rect, Scalar(0,0,255), 3);//对外轮廓加矩形框 
        }   
         imshow("Contours on white image",result);  
         cvWaitKey(0);
         //draw contours on the original image 
         Mat original=imread(img_name); 
         int index_ori = 0;  
         for (; index_ori >= 0; index_ori = hierarchy[index_ori][0]) 
         {
             Scalar color(rand() & 255, rand() & 255, rand() & 255);  
             //描绘字符的外轮廓
             drawContours(original,contours,index_ori,Scalar(255),1,8, hierarchy);  
             Rect rect = boundingRect(contours[index_ori]);//检测外轮廓
             //对外轮廓加加矩形框 
             rectangle(original, rect, Scalar(0,0,255), 3);  
        }
        //print contours info
        cout<<"The number of external contours:"<<contours.size()<<endl;
        imshow("Contours on original image",original);  
        waitKey(0);
         return 0;
    }

二、程序运行效果图：

(1)源图像:

![这里写图片描述][SouthEast]、  
(2)灰度图像：  
![这里写图片描述][SouthEast 1]  
(3)二进制图像：  
![这里写图片描述][SouthEast 2]  
(4)轮廓在空白图像上显示：  
![这里写图片描述][SouthEast 3]  
(5)在原图像上画出图像的轮廓以及外接矩形：  
![这里写图片描述][SouthEast 4]  
至此，图像的轮廓检测以及外接矩形已经实现，欢迎高人指正。

[SouthEast]: /images/20220612/8915ad8b152043db854f35115d542d8b.png
[SouthEast 1]: /images/20220612/33283143ce5a4f30b38b845d115eef85.png
[SouthEast 2]: /images/20220612/5c1b88d70bd44b98a1c15f0439d357f4.png
[SouthEast 3]: /images/20220612/55530d1312384fa7a2e9e57bc6887ce7.png
[SouthEast 4]: /images/20220612/c020817023044cb7bf90d9459b846677.png