理论

图像变换可以看作如下：

• 像素变换 – 点操作
• 邻域操作 – 区域
  调整图像亮度和对比度属于像素变换-点操作
  

API

• saturate_cast(value)确保值大小范围为0~255之间
• Mat.at(y,x)[index]=value 给每个像素点每个通道赋值

代码

#include <opencv2/opencv.hpp>
#include <iostream>using namespace cv;
int main(int argc, char** argv) {Mat src, dst;src = imread("test.png");if (!src.data) {printf("could not load image...\n");return -1;}char input_win[] = "input image";cvtColor(src, src, CV_BGR2GRAY);namedWindow(input_win);imshow(input_win, src);// contrast and brigthtness changes int height = src.rows;int width = src.cols;dst = Mat::zeros(src.size(), src.type());float alpha = 1.2;float beta = 30;Mat m1;src.convertTo(m1, CV_32F);for (int row = 0; row < height; row++) {for (int col = 0; col < width; col++) {if (src.channels() == 3) {float b = m1.at<Vec3f>(row, col)[0];// bluefloat g = m1.at<Vec3f>(row, col)[1]; // greenfloat r = m1.at<Vec3f>(row, col)[2]; // red// outputdst.at<Vec3b>(row, col)[0] = saturate_cast<uchar>(b*alpha + beta);dst.at<Vec3b>(row, col)[1] = saturate_cast<uchar>(g*alpha + beta);dst.at<Vec3b>(row, col)[2] = saturate_cast<uchar>(r*alpha + beta);}else if (src.channels() == 1) {float v = src.at<uchar>(row, col);dst.at<uchar>(row, col) = saturate_cast<uchar>(v*alpha + beta);}}}char output_title[] = "contrast and brightness change demo";namedWindow(output_title);imshow(output_title, dst);waitKey(0);return 0;
}