OpenCV |动手图像亮度

亮度意味着更改每个图像像素的值。可以通过以任何常数增加或减少图像的像素值来完成此更改。本文深入介绍了如何使用OpenCV更改图像亮度。

Input : 
Original Image

Output : 
-> Original Image
-> Image with brightness increased by 100
-> Image with brightness increased by 50
-> Image with brightness decreased by 100
-> Image with brightness decreased by 50

代码：CPP代码以控制图像亮度

// c++ code explaining how to
// increase or decrease the brightness of
// an image
  
// loading library files
#include 
#include 
#include 
  
using namespace cv;
using namespace std;
  
int main(int argc, char** argv)
{
    // Loading the Image File under testing
    Mat image = imread("C:\\Users\\dell\\Desktop\\abc.jpg");
  
    // Check whether the image is present or not
    if (image.empty()) {
        cout << "Could not open or find the image" << endl;
  
        // waiting for any  key to be pressed
        return -1;
    }
  
    // Declaring the Brightness Instances
  
    Mat imageBrighnessHigh50;
    // increasing the brightness level by 50
    image.convertTo(imageBrighnessHigh50, -1, 1, 50);
  
    Mat imageBrighnessHigh100;
    // increasing the brightness level by 100
    image.convertTo(imageBrighnessHigh100, -1, 1, 100);
  
    Mat imageBrighnessLow50;
    // decreasing the brightness level by 50
    image.convertTo(imageBrighnessLow50, -1, 1, -50);
  
    Mat imageBrighnessLow100;
    // decreasing the brightness level by 100
    image.convertTo(imageBrighnessLow100, -1, 1, -100);
  
    // Declaring the windows
    // for images belonging to different brightness level
    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";
  
    // Running the window instance
    // and opening it
    namedWindow(windowNameOriginalImage, WINDOW_NORMAL);
    namedWindow(windowNameBrightnessHigh50, WINDOW_NORMAL);
    namedWindow(windowNameWithBrightnessHigh100, WINDOW_NORMAL);
    namedWindow(windowNameBrightnessLow50, WINDOW_NORMAL);
    namedWindow(windowNameBrightnessLow100, WINDOW_NORMAL);
  
    // Loading images inside the above created Windows
    imshow(windowNameOriginalImage, image);
    imshow(windowNameBrightnessHigh50, imageBrighnessHigh50);
    imshow(windowNameWithBrightnessHigh100, imageBrighnessHigh100);
    imshow(windowNameBrightnessLow50, imageBrighnessLow50);
    imshow(windowNameBrightnessLow100, imageBrighnessLow100);
  
    // waiting for any key to be pressed
    waitKey(0);
  
    // closing all the windows instances
    // when any key is pressed.
    destroyAllWindows();
  
    return 0;
}

输入 ：

输出 ：
原始图片

亮度等级提高50

亮度等级提高100

亮度等级降低50

亮度等级降低100

解释 ：

// Declaring the Brightness Instances
  
Mat imageBrighnessHigh50;
// increasing the brightness level by 50
image.convertTo(imageBrighnessHigh50, -1, 1, 50);
  
Mat imageBrighnessHigh100;
// increasing the brightness level by 100
image.convertTo(imageBrighnessHigh100, -1, 1, 100);
  
Mat imageBrighnessLow50;
// decreasing the brightness level by 50
image.convertTo(imageBrighnessLow50, -1, 1, -50);
  
Mat imageBrighnessLow100;
// decreasing the brightness level by 100
image.convertTo(imageBrighnessLow100, -1, 1, -100);

这些代码行会将图像像素值更改指定的数量。然后将最终更改的图像存储到给定的输出图像。如果指定的量为正(上面的值为50)，则亮度级别将增加；否则，如果指定的量为负，则亮度级别将降低。

MAT函数：
“ MAT”函数将每个图像像素值更改为目标数据类型，并根据增加或减少值进行更改。

Parameters : 

m      : Output Image 
rtype  : Output Image type, Output Image type is same as input
         if it is set to -ve value
alpha  : Input image pixel are multiplied with this number prior
         to its assignment to output image
beta   : adding this value to each input image pixel 

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