如果你想提升一幅图像的亮度，可以给每个像素的值都加上一个正的常数
\[ new\_image (i, j) = image(i, j) + c \]
如果你想降低一幅图像的亮度，可以给每个像素的值都减去一个正的常数
\[ new\_image (i, j) = image(i, j) - c \]
Code
/*
作者：郑大峰
时间：2019年09月20日
环境：OpenCV 4.1.1 + VS2017
内容：Change Brightness
*/
#include "pch.h"
#include <iostream>
#include <opencv2/opencv.hpp>
using namespace std;
using namespace cv;
int main()
{
Mat image = imread("claudia.png");
if (image.empty())
{
cout << "Could not open or find the image" << endl;
cin.get();
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;
}
Result
Explanation
void Mat::convertTo( OutputArray m, int rtype, double alpha=1, double beta=0 ) const
This function converts the each pixel value to the target data type and changes the value as per the following formula. pixel_value_of_output_image(x, y) = pixel_value_of_input_image(x, y) * alpha + beta;
m - Output image. This data structure will be reallocated if required.rtype - Type of the output image. If rtype is a negative value, the type of the output image will be same as the input image.alpha - Each pixels in the input image will be multiplied by this number before assigning to the output image.beta - This value will be added to each pixels in the input image and assigned to the output image.
转载于:https://www.cnblogs.com/zdfffg/p/11558123.html
