一、理论

 亮度：0~255之间取大一些的值

对比度：即让R G B 分量的差值增大

二、代码演示

#include<opencv2\opencv.hpp>
#include<iostream>
#include<math.h>
using namespace cv;
using namespace std;
int main()
{Mat src = imread("E:\\vs2015\\opencvstudy\\3.jpg", 1);if (!src.data){cout << "could not load image1!" << endl;return -1;}char input_win[] = "input image";imshow(input_win, src);cvtColor(src, src, CV_BGR2GRAY);//Vec3b 到 Vec3f 的转换函数 src.convertTo()Mat m1;src.convertTo(m1, CV_32F);int height = src.rows;int width = src.cols;Mat dst = Mat::zeros(src.size(), src.type());double alpha = 0.6; //控制对比度float beta = 10;  //控制亮度for (int row = 0; row < height; row++){for (int col = 0; col < width; col++){if (src.channels() == 3){/*int b = src.at<Vec3b>(row,col)[0];  这里直接使用Vec3f会报错。不可以强转int g = src.at<Vec3b>(row,col)[1];int r = src.at<Vec3b>(row,col)[2];*/float b = m1.at<Vec3f>(row, col)[0];float g = m1.at<Vec3f>(row, col)[1];float r = m1.at<Vec3f>(row, col)[2];dst.at<Vec3b>(row, col)[0] = saturate_cast<uchar>(alpha *b + beta);dst.at<Vec3b>(row, col)[1] = saturate_cast<uchar>(alpha*g + beta);dst.at<Vec3b>(row, col)[2] = saturate_cast<uchar>(alpha*r + beta);}else if (src.channels() == 1){float pixel = src.at<uchar>(row, col);dst.at<uchar>(row, col) = saturate_cast<uchar>(alpha*pixel + beta);}else {cout << "ERROR" << endl;}}}char output_title[] = "contrast and brightness change demo";imshow(output_title, dst);waitKey(0);return 0;
}