前兩篇博文分別介紹了影象的邊緣檢測和輪廓檢測，本文接著介紹影象的輪廓檢測和輪廓外接矩形：

一、程式碼部分：

// extract_contours.cpp : 定義控制檯應用程式的入口點。
//
#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);//轉換成2值影象  
 

    imshow("binary",gray); 
    cvWaitKey(0);
    // Detecting contours 
    vector<vector<Point>> contours;  //定義輪廓集合  
    vector<Vec4i> hierarchy; 
    findContours(gray, contours, hierarchy, CV_RETR_EXTERNAL, CV_CHAIN_APPROX_NONE);//CV_RETR_EXTERNAL只檢測外部輪廓
    // 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]表示後一個輪廓
    {  
        Scalar color(rand() & 255, rand() & 255, rand() & 255);  
        drawContours(result, contours, index, Scalar(0), 1, 8, hierarchy);//描繪字元的外輪廓  
        Rect rect = boundingRect(contours[index]);//檢測外輪廓  
        rectangle(result, rect, Scalar(0,0,255), 3);//對外輪廓加矩形框  
    }   
     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);  
         //描繪字元的外輪廓
         drawContours(original,contours,index_ori,Scalar(255),1,8, hierarchy);  
         Rect rect = boundingRect(contours[index_ori]);//檢測外輪廓
         //對外輪廓加加矩形框  
         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、程式執行效果圖：

(1)源影象:

、
(2)灰度影象：

(3)二進位制影象：

(4)輪廓在空白影象上顯示：

(5)在原影象上畫出影象的輪廓以及外接矩形：

至此，影象的輪廓檢測以及外接矩形已經實現，歡迎高人指正。