文章目录
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
c
#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];// 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[] = "contrast and brightness change demo";
namedWindow(output_title);
imshow(output_title, dst);
waitKey(0);
return 0;
}