1、图像亮度和对比度理论部分
注:图片来自51CTO学院网课
2、处理步骤
先将图片处理成(0,0,0)的黑色图片,然后再根据像素变换操作进行处理:
处理三通道:
1、分别对每个通道进行像素变换操作
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];// blue
float g = m1.at<Vec3f>(row, col)[1]; // green
float r = m1.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);
}
处理单通道:
1.先将一张三通道彩色图片转换成灰度图像
2.对灰度图像进行像素变换操作
float v = src.at<uchar>(row, col);
dst.at<uchar>(row, col) = saturate_cast<uchar>(v * alpha + beta);
代码:
#include <opencv2/opencv.hpp>
#include <iostream>
using namespace cv;
using namespace std;
void Myshow(string name, const Mat& result);
int main() {
Mat src, dst;
src = imread("F:\\opencv_work\\07增强亮度和对比度\\Project1\\18.jpg");
if (src.empty()) {
printf("could not load image...\n");
return -1;
}
char input_win[] = "输入图片";
cvtColor(src, src, COLOR_BGR2GRAY);
namedWindow(input_win, WINDOW_AUTOSIZE);
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];// blue
float g = m1.at<Vec3f>(row, col)[1]; // green
float r = m1.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[] = "舵主的增强亮度和对比度图片";
/*namedWindow(output_title, WINDOW_AUTOSIZE);
imshow(output_title, dst);*/
Myshow(output_title, dst);
waitKey(0);
return 0;
}
void Myshow(string name, const Mat& result)
{
namedWindow(name, WINDOW_FREERATIO);
imshow(name, result);
}