OpenCV实现图像轮廓检测以及外接矩形

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:

(2)灰度图像:

(3)二进制图像:

(4)轮廓在空白图像上显示:

(5)在原图像上画出图像的轮廓以及外接矩形:

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。

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