使用inRange进行阈值操作

比眉伴天荒 2022-04-02 15:36 228阅读 0赞

## HSV色域空间 ##

*  Hue（色调）：色彩的基本属性，就是平常说的颜色的名称，如红色、黄色等
 *  Saturation（饱和度）：色彩的纯度，越高色彩越纯，低则逐渐变灰，取0-100%的数值。
 *  Value（亮度值）：描述的是色彩的亮度，取值0-1，0 就是黑色，1（饱和度为0）为白色。

![20181227103051955.jpg][]

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## 官方代码 ##

#include <opencv2/opencv.hpp>
    #include <iostream>
    
    using namespace cv;
    using namespace std;
    
    
    const int max_value_H = 360/2; //因为进行8位存储，所以除以2
    const int max_value = 255; 
    
    const cv::String window_capture_name = "Video Capture";
    const cv::String window_detection_name = "Object Detection";
    
    int low_H = 0, low_S = 0, low_V = 0;
    int high_H = max_value_H, high_S = max_value, high_V = max_value;
    
    
    static void on_low_H_thresh_trackvbar(int, void*)
    { 
    	low_H = min(high_H-1,low_H);//防止最大值小于最小值
    	setTrackbarPos("Low H",window_detection_name,low_H);
    }
    
    
    static void on_high_H_thresh_trackbar(int, void*)
    { 
    	high_H = max(high_H, low_H+1);
    	setTrackbarPos("High H",window_detection_name,high_H);
    }
    
    static void on_low_S_thresh_trackbar(int, void*)
    { 
    	low_S = min(high_S-1, low_S);
    	setTrackbarPos("Low S",window_detection_name,low_S);
    }
    
    static void on_high_S_thresh_trackbar(int, void*)
    { 
    	high_H = max(high_S,low_S+1);
    	setTrackbarPos("High S",window_detection_name,high_S);
    }
    
    static void on_low_V_thresh_trackbar(int, void*)
    { 
    	low_V = min(high_V-1, low_V);
    	setTrackbarPos("Low V",window_detection_name,low_V);
    	
    }
    
    
    static void on_high_V_thresh_trackvar(int, void*)
    { 
    	high_V = max(high_V,low_V+1);
    	setTrackbarPos("High V",window_detection_name,high_V);
    }
    
    
    int main(void)
    { 
    	
    	VideoCapture cap(0); //打开摄像头
    	namedWindow(window_capture_name);
    	namedWindow(window_detection_name);
    
    
    	createTrackbar("Low H",window_detection_name,&low_H,max_value_H,on_high_H_thresh_trackbar);
    	createTrackbar("High H",window_detection_name,&high_H,max_value_H,on_high_H_thresh_trackbar);
    
    	createTrackbar("Low S",window_detection_name,&low_S,max_value,on_low_S_thresh_trackbar);
    	createTrackbar("High S",window_detection_name,&high_S,max_value,on_high_S_thresh_trackbar);
    
    	createTrackbar("Low V",window_detection_name,&low_V,max_value,on_low_V_thresh_trackbar);
         createTrackbar("High V",window_detection_name,&high_V,max_value,on_high_V_thresh_trackvar);
    	
    	Mat frame, frame_HSV, frame_threshold;
    	while(true)
    	{ 
    		cap >> frame;   //捕获的每帧给frame
    		if(frame.empty())
    		{ 
    			break;
    		}
    
    		cv::cvtColor(frame,frame_HSV,cv::COLOR_BGR2HSV); //转化到HSV空间
    
    //进行阈值操作，输出图像为CV_8UC1
    		inRange(frame_HSV,Scalar(low_H,low_S,low_V),Scalar(high_H,high_S,high_V),frame_threshold);
    
    		imshow(window_capture_name,frame);
    		imshow(window_detection_name,frame_threshold);
    
    		char key=(char)waitKey(30); //每等待30ms，如果是ESC，退出
    		if(key == 27)
    			break;
    	}
    	return 0;
    };

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

结果：

![在这里插入图片描述][20181227105924529.png]

## OpenCV API ##

void cv::inRange  
(  
InputArray src,    //输入图像  
InputArray lowerb,    //低阈值  
InputArray upperb,    //高阈值  
OutputArray dst     //输出图像（same size as src），**CV\_8UC1**  
)

dst(i) 为1，如果输入图像的像素在lowerb和upperb形成的 1D，2D，3D的box里面，否则为0，

比如1D，则lowerb和upperb只是一维值，如果是3D，则lowerb和upperb只是三维值，输入图像也是三维，只要每个元素再lowerb和upperb组成的3D box里面，输出就是1，所以输出是CV\_8UC1

[20181227103051955.jpg]: /images/20220402/3aa3db9359824b9a87b0685610886689.png
[20181227105924529.png]: /images/20220402/45fca9070e7d4d38ac7c2efdaf3cf939.png