灰度变换原理//test later

灰度变换原理

图像灰度变换变换原理：通过变换函数T将原图像像素灰度值r映射为灰度值s：

2、灰度反转

2.1原理

灰度反转：将图像亮暗对调，可以增强图像中暗色区域细节

�=�(�)=�−1−�

其中L为图像灰度级，0~255灰度图像的灰度级为256.

2.2 c++ opencv代码

#include<iostream>
#include<opencv2/opencv.hpp>using namespace cv;
using namespace std;int main()
{ Mat image1, output_image, image1_gray;   //定义输入图像，输出图像，灰度图像image1 = imread("lena.png");  //读取图像；if (image1.empty()){cout << "读取错误" << endl;return -1;}cvtColor(image1, image1_gray, COLOR_BGR2GRAY);  //灰度化imshow(" image1_gray", image1_gray);   //显示灰度图像output_image = image1_gray.clone();for (int i = 0; i < image1_gray.rows; i++){for (int j = 0; j < image1_gray.cols; j++){output_image.at<uchar>(i, j) = 255 - image1_gray.at<uchar>(i, j);  //灰度反转}}imshow("output_image", output_image);  //显示反转图像waitKey(0);  //暂停，保持图像显示，等待按键结束return 0;
}

结果：

3、对数变换

3.1原理

对数变换：扩展图像中的暗像素值，压缩高灰度值。

�=�(�)=�∗��(1+�)

3.2 c++ opencv

#include<iostream>
#include<opencv2/opencv.hpp>using namespace cv;
using namespace std;int main()
{ Mat image1, output_image, image1_gray;   //定义输入图像，输出图像，灰度图像image1 = imread("lena.png");  //读取图像；if (image1.empty()){cout << "读取错误" << endl;return -1;}cvtColor(image1, image1_gray, COLOR_BGR2GRAY);  //灰度化imshow(" image1_gray", image1_gray);   //显示灰度图像output_image = image1_gray.clone();for (int i = 0; i < image1_gray.rows; i++){for (int j = 0; j < image1_gray.cols; j++){output_image.at<uchar>(i, j) =6*log((double)(image1_gray.at<uchar>(i, j))+1);  //对数变换 s=6*log(r+1)}}normalize(output_image, output_image, 0, 255, NORM_MINMAX);  //图像归一化，转到0~255范围内convertScaleAbs(output_image, output_image);  //数据类型转换到CV_8Uimshow(" output_image", output_image);  //显示变换图像waitKey(0);  //暂停，保持图像显示，等待按键结束return 0;
}

结果：

4、幂律（伽马变换）

4.1原理

幂律变换与对数变换类似：

4.2 c++ opencv代码

#include<iostream>
#include<opencv2/opencv.hpp>using namespace cv;
using namespace std;int main()
{ Mat image1, output_image, image1_gray;   //定义输入图像，输出图像，灰度图像image1 = imread("lena.png");  //读取图像；if (image1.empty()){cout << "读取错误" << endl;return -1;}cvtColor(image1, image1_gray, COLOR_BGR2GRAY);  //灰度化imshow(" image1_gray", image1_gray);   //显示灰度图像output_image = image1_gray.clone();for (int i = 0; i < image1_gray.rows; i++){for (int j = 0; j < image1_gray.cols; j++){output_image.at<uchar>(i, j) =6*pow((double)image1_gray.at<uchar>(i, j),0.5);  //幂律变换 s=6*r^0.5}}normalize(output_image, output_image, 0, 255, NORM_MINMAX);  //图像归一化，转到0~255范围内convertScaleAbs(output_image, output_image);  //数据类型转换到CV_8Uimshow(" output_image", output_image);  //显示变换图像waitKey(0);  //暂停，保持图像显示，等待按键结束return 0;
}

结果：