Gamma校正及其实现

来源：互联网发布：rmvb转mp4软件编辑：程序博客网时间：2024/05/16 09:17

图2中左图为原图，中图为gamma = 1/2.2在校正结果，原图中左半侧的灰度值较高，右半侧的灰度值较低，经过gamma = 1/2.2校正后(中图)，左侧的对比度降低(见胡须)，右侧在对比度提高(明显可以看清面容)，同时图像在的整体灰度值提高。

右图为gamma = 2.2在校正结果，校正后，左侧的对比度提高(见胡须)，右侧在对比度降低(面容更不清楚了)，同时图像在的整体灰度值降低。

值得一提的是，人眼是按照gamma < 1的曲线对输入图像进行处理的。

参考资料：

[1] http://en.wikipedia.org/wiki/Gamma_correction

[2] http://www.cambridgeincolour.com/tutorials/gamma-correction.htm

[3] https://github.com/bytefish/opencv/blob/master/misc/tan_triggs.cpp

代码:

#include <opencv2/core/core.hpp>#include <opencv2/imgproc/imgproc.hpp>#include <opencv2/highgui/highgui.hpp> #include <iostream> using namespace cv;using namespace std;// Normalizes a given image into a value range between 0 and 255.Mat norm_0_255(const Mat& src) {    // Create and return normalized image:    Mat dst;    switch(src.channels()) {    case 1:        cv::normalize(src, dst, 0, 255, NORM_MINMAX, CV_8UC1);        break;    case 3:        cv::normalize(src, dst, 0, 255, NORM_MINMAX, CV_8UC3);        break;    default:        src.copyTo(dst);        break;    }    return dst;}int main(int argc, const char *argv[]) {    // Get filename to the source image:    if (argc != 2) {        cout << "usage: " << argv[0] << " <image.ext>" << endl;        exit(1);    }    // Load image & get skin proportions:    //Mat image = imread(argv[1], CV_LOAD_IMAGE_GRAYSCALE);Mat image = imread(argv[1], CV_LOAD_IMAGE_COLOR);    // Convert to floating point:    Mat X;image.convertTo(X, CV_32FC1);//image.convertTo(X, CV_32F);    // Start preprocessing:    Mat I;float gamma = 1/2.2;    pow(X, gamma, I);    // Draw it on screen:    imshow("Original Image", image);    imshow("Gamma correction image", norm_0_255(I));//imwrite("origin.jpg", image);imwrite("gamma_inv2.2.jpg", norm_0_255(I));    // Show the images:    waitKey(0);    // Success!    return 0;}

6 0