改变图像的明度和对比度

Brightness

    #include 
    #include 
    
    using namespace cv;
    using namespace std;
    
    int main(int argc, char** argv)
    {
    	// Read the image file
    	Mat image = imread("/home/CORPUSERS/xp025362/Pictures/st.jpeg");
    
    	// Check for failure
    	if (image.empty())
    	{
    		cout << "Could not open or find the image" << endl;
    		cin.get(); //wait for any key press
    		return -1;
    	}
    
    	Mat imageBrighnessHigh50;
    	image.convertTo(imageBrighnessHigh50, -1, 1, 50); //increase the brightness by 50
    
    	Mat imageBrighnessHigh100;
    	image.convertTo(imageBrighnessHigh100, -1, 1, 100); //increase the brightness by 100
    
    	Mat imageBrighnessLow50;
    	image.convertTo(imageBrighnessLow50, -1, 1, -50); //decrease the brightness by 50
    
    	Mat imageBrighnessLow100;
    	image.convertTo(imageBrighnessLow100, -1, 1, -100); //decrease the brightness by 100
    
    	//Defining window names for above images
    	String windowNameOriginalImage = "Original Image";
    	String windowNameBrightnessHigh50 = "Brightness Increased by 50";
    	String windowNameWithBrightnessHigh100 = "Brightness Increased by 100";
    	String windowNameBrightnessLow50 = "Brightness Decreased by 50";
    	String windowNameBrightnessLow100 = "Brightness Decreased by 100";
    
    	//Create and open windows for above images
    	namedWindow(windowNameOriginalImage, WINDOW_NORMAL);
    	namedWindow(windowNameBrightnessHigh50, WINDOW_NORMAL);
    	namedWindow(windowNameWithBrightnessHigh100, WINDOW_NORMAL);
    	namedWindow(windowNameBrightnessLow50, WINDOW_NORMAL);
    	namedWindow(windowNameBrightnessLow100, WINDOW_NORMAL);
    
    	//Show above images inside the created windows.
    	imshow(windowNameOriginalImage, image);
    	imshow(windowNameBrightnessHigh50, imageBrighnessHigh50);
    	imshow(windowNameWithBrightnessHigh100, imageBrighnessHigh100);
    	imshow(windowNameBrightnessLow50, imageBrighnessLow50);
    	imshow(windowNameBrightnessLow100, imageBrighnessLow100);
    
    	waitKey(0); // Wait for any key stroke
    
    	destroyAllWindows(); //destroy all open windows
    
    	return 0;
    }

PS: 这里为什么是明度而不是亮度，请大家自行google。然后看下效果图(从左往右，至上而下的顺序，依次为原始img, +50, +100, -50 ,-100)：

Contrast

    #include 
    #include 
    
    using namespace cv;
    using namespace std;
    
    int main(int argc, char** argv)
    {
    	// Read the image file
    	Mat image = imread("/home/CORPUSERS/xp025362/Pictures/st.jpeg");
    
    	// Check for failure
    	if (image.empty())
    	{
    		cout << "Could not open or find the image" << endl;
    		cin.get(); //wait for any key press
    		return -1;
    	}
    
    	Mat imageContrastHigh2;
    	image.convertTo(imageContrastHigh2, -1, 2, 0); //increase the contrast by 2
    
    	Mat imageContrastHigh4;
    	image.convertTo(imageContrastHigh4, -1, 4, 0); //increase the contrast by 4
    
    	Mat imageContrastLow0_5;
    	image.convertTo(imageContrastLow0_5, -1, 0.5, 0); //decrease the contrast by 0.5
    
    	Mat imageContrastLow0_25;
    	image.convertTo(imageContrastLow0_25, -1, 0.25, 0); //decrease the contrast by 0.25
    
    
    	//Defining window names for above images
    	String windowNameOriginalImage = "Original Image";
    	String windowNameContrastHigh2 = "Contrast Increased by 2";
    	String windowNameContrastHigh4 = "Contrast Increased by 4";
    	String windowNameContrastLow0_5 = "Contrast Decreased by 0.5";
    	String windowNameContrastLow0_25 = "Contrast Decreased by 0.25";
    
    	//Create and open windows for above images
    	namedWindow(windowNameOriginalImage, WINDOW_NORMAL);
    	namedWindow(windowNameContrastHigh2, WINDOW_NORMAL);
    	namedWindow(windowNameContrastHigh4, WINDOW_NORMAL);
    	namedWindow(windowNameContrastLow0_5, WINDOW_NORMAL);
    	namedWindow(windowNameContrastLow0_25, WINDOW_NORMAL);
    
    	//Show above images inside the created windows.
    	imshow(windowNameOriginalImage, image);
    	imshow(windowNameContrastHigh2, imageContrastHigh2);
    	imshow(windowNameContrastHigh4, imageContrastHigh4);
    	imshow(windowNameContrastLow0_5, imageContrastLow0_5);
    	imshow(windowNameContrastLow0_25, imageContrastLow0_25);
    
    	waitKey(0); // Wait for any key stroke
    
    	destroyAllWindows(); //destroy all open windows
    
    	return 0;
    }

同样看下效果图（同上）：

例子很简单，看下convertTo的使用，相信大家也看出来了，alpha其实就是前面说的对比度，beta就是前面说的明度。

PS：想起以前同学经常看得一本经典的入门书籍《数字图像处理》冈萨写的，我是没有看过，推荐大家有时间可以看下，很多概念很有意思，与君共勉～