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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;

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