006-Opencv笔记-调整图像亮度和对比度

理论公式

f(i,j)是输入图像的像素点，g(i,j)是输出图像的像素点，

亮度和对比度属于像素变换

#include "pch.h"
#include <opencv2/opencv.hpp>
#include <iostream>

using namespace cv;

//图像亮度，对比度
int main(int argc, char** argv) {
    Mat src, dst;
    src = imread("D:/test.jpg");
    if (!src.data) {
        printf("could not load image...\n");
        return -1;
    }
    char input_win[] = "原图";
    //cvtColor(src, src, CV_BGR2GRAY);//灰度图
    namedWindow(input_win, CV_WINDOW_AUTOSIZE);
    imshow(input_win, src);

    // contrast and brigthtness changes | 对比度和亮度变化
    int height = src.rows;
    int width = src.cols;
    dst = Mat::zeros(src.size(), src.type());
    float alpha = 2.1;//对比度
    float beta = 30;//增量-亮度

    src.convertTo(src, CV_32F);//将CV_8UC1/3转成Vec3f 精度更高点
    for (int row = 0; row < height; row++) {
        for (int col = 0; col < width; col++) {

            if (src.channels() == 3) {
                float b = src.at<Vec3f>(row, col)[0];// blue
                float g = src.at<Vec3f>(row, col)[1]; // green
                float r = src.at<Vec3f>(row, col)[2]; // red

                // output
                dst.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[] = "test6";
    namedWindow(output_title, CV_WINDOW_AUTOSIZE);
    imshow(output_title, dst);

    waitKey(0);
    return 0;
}