阈值操作

左手的ㄟ右手 2022-04-03 06:54 214阅读 0赞

## 阈值操作 ##

*  OpenCV 提供了 [cv::threshold][cv_threshold]，一共有5种不同的阈值操作  
      
      
    蓝色的横线表示阈值, 红色表示像素值

![2018122017315247.png][]

1.  Threshold Binary

![20181220205222716.png][]

1.  Threshold Binary, Inverted

![20181220205401970.png][]

1.  Truncate

![20181220205449286.png][]

1.  Threshold to Zero

![20181220205538232.png][]

1.  Threshold to Zero, Inverted

![20181220205720768.png][]

--------------------

## 代码 ##

#include <opencv2/opencv.hpp>
    #include <iostream>
    
    using namespace cv;
    using namespace std;
    
    //trackbar 初始值和最大值
    int threshold_value = 0;
    int threshold_type = 3;
    int const max_value = 255;
    int const max_type =4;
    
    
    int const max_pixel_value =255;
    
    // trackbar的名字
    const char* trackbar_type = "Type: \n 0:Binary\n1: Binary Inverted\n2:Truncate \n3:To zero\n4:Zero Inverted";
    const char* trackbar_value = "Value";
    
    String window_name("Threshold_Demo");
    String image_name("../res/beauty.jpg");
    
    Mat src,dst,src_gray;
    
    
    void Threshold_Demo(int arg1, void* arg2);
    
    int main(void)
    { 
    	
        src = imread(image_name);
    	if(src.empty())
    	{ 
    		cout << "can't load the image" << endl;
    	}
    
    
    	cv::cvtColor(src,src_gray,cv::COLOR_BGR2GRAY);
    	cv::namedWindow(window_name,cv::WINDOW_AUTOSIZE);
    
    
    	cv::createTrackbar(trackbar_type,window_name,&threshold_type,max_type,Threshold_Demo);
    	cv::createTrackbar(trackbar_value,window_name,&threshold_value,max_value,Threshold_Demo);
    	
    
    
    	Threshold_Demo(0,0);
    	waitKey();
    	return 0;
    };
    
    
    void Threshold_Demo(int arg1, void* arg2)
    { 
    	threshold(src_gray,dst,threshold_value,max_pixel_value,threshold_type);
    	imshow(window_name,dst);
    }

结果：  
![在这里插入图片描述][20181221103938728.png]

--------------------

## OpenCV API ##

1.  double [cv::threshold][cv_threshold]  
    (  
    InputArray src,  
    OutputArray dst,  
    double thresh,    // 阈值  
    double maxval,    // 最大值  
    int type ,    // 阈值处理的类型，上面5种方式  
    )

1.  int [cv::createTrackbar ][cv_createTrackbar]  
    (  
    const String & trackbarname,  
    const String & winname,  
    int \* value,     // 初始值  
    int count,     //最大值  
    TrackbarCallback onChange = 0, //回调函数名（必须申明成 void Foo(int,void\*); ）  
    void \* userdata = 0  
    )

[cv_threshold]: https://docs.opencv.org/master/d7/d1b/group__imgproc__misc.html#gae8a4a146d1ca78c626a53577199e9c57
[2018122017315247.png]: /images/20220403/aa77460e14d04ed99a514ff73cdfbaf3.png
[20181220205222716.png]: /images/20220403/fa9f83bb70b748ce8bfcd65455176a24.png
[20181220205401970.png]: /images/20220403/e8aaea0e35374dff83961943a16c0e84.png
[20181220205449286.png]: /images/20220403/2295358f0e65460a96b9299addf7ae8a.png
[20181220205538232.png]: /images/20220403/4635578ac27c4b2880f2acdce9fdbde2.png
[20181220205720768.png]: /images/20220403/5e8689e5ca734111882668bd9385b15e.png
[20181221103938728.png]: /images/20220403/953b95bfca0344fea47d65e672c55998.png
[cv_createTrackbar]: https://docs.opencv.org/master/d7/dfc/group__highgui.html#gaf78d2155d30b728fc413803745b67a9b