图像亮度和对比度调整

╰半橙微兮° 2022-04-12 05:42 369阅读 0赞

### 文章目录 ###

*   *  alpha, beta correction
     *  gamma correction

## alpha, beta correction ##

*  原理： g ( i , j ) = α ⋅ f ( i , j ) + β g(i,j)=α⋅f(i,j)+β g(i,j)=α⋅f(i,j)\+β  
    α：>0，gain parameters ,改变对比度（contrast）  
    β： bias parameters ，改变亮度（brightness）

*  代码

#include <opencv2/opencv.hpp>
    #include <iostream>
    
    
    using namespace cv;
    using namespace std;
    
    
    int main(void)
    { 
    
    	Mat origin = imread("../res/lena.jpeg");
    
    	if(origin.empty())
    	{ 
    		cout << "could not find the image,please confirm the path"<< endl;
    		return -1;
    	}
    
    	Mat dst=Mat::zeros(origin.size(),origin.type());
    	double alpha =2.2;
    	int beta = 50;
    
    	uchar* pOrigin;
    	uchar* pDst;
    
    	int col=origin.cols*3,row=origin.rows;
    
    	if(origin.isContinuous())
    	{ 
    		col=origin.cols*3*origin.rows;
    		row =1;
    	}
    
    
    	for(int i=0; i<row; i++)
    	{ 
    		pOrigin = origin.ptr<uchar>(i);
    		pDst = dst.ptr(i);
    		
    		for(uint j=0; j<col; j++)
    		{ 
    			pDst[j] =saturate_cast<uchar>(alpha*(pOrigin[j])+beta);
    		}
    
    	}
    
    	imshow("Origin_Image",origin);
    	imshow("New Image",dst);
    	waitKey();
    	return 0;
    }

结果：alpha=2.2   beta = 50  
![在这里插入图片描述][20181201190948510.png]

![在这里插入图片描述][20181201191025813.png]

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

## gamma correction ##

*  原理：将输入**非线性映射**到输出： O = ( I 255 ) γ × 255 O=(\\frac\{I\}\{255\})^γ×255 O=(255I)γ×255

![在这里插入图片描述][20181201191907214.png]

*  代码：

int main(void)
    { 
    	double gamma=3;
    	Mat origin = imread("../res/image.png");
    
    	if(origin.empty())
    	{ 
    		cout << "could not find the image,please confirm the path"<< endl;
    		return -1;
    	}
    
    
    	Mat LookupTable(1,256,CV_8U);
    	uchar*p = LookupTable.data;
    
    	for(int i=0; i<256; i++)
    	{ 
    		p[i] = saturate_cast<uchar>(pow(i/255.0,gamma)*255.0);
    	}
    	
    	Mat dst =origin.clone();
    	LUT(origin,LookupTable,dst);
    
    
    	imshow("Origin_Image",origin);
    	imshow("New_Image",dst);
    	// imwrite("../res/image_new.png",dst);
    	waitKey();
    
    	return 0;
    
    }

*  结果：

![原图][20181201195659362.png]

原图  
![gamma=0.4 处理之后][gamma_0.4]  
gamma=0.4

![alpha=1.3 beta=40][alpha_1.3 beta_40]  
alpha=1.3 beta=40  
 α β \\alpha \\beta αβ矫正也可以提高对比度，亮度，但是云的细节消失了。

[20181201190948510.png]: /images/20220412/7c912c43863a412db6fe1c9830c51ba9.png
[20181201191025813.png]: /images/20220412/63c43fcd20b34e32ace8010325965f6a.png
[20181201191907214.png]: /images/20220412/0e8476f29a4749408b5c506c30b9b509.png
[20181201195659362.png]: /images/20220412/8c767018d39a4ad2ab03967e6268011a.png
[gamma_0.4]: /images/20220412/4f543c973f0b44dfa4f1c8f83d8756b1.png
[alpha_1.3 beta_40]: /images/20220412/e71bd69d008a41b08d29bec5536062ee.png