17、OpenCV灰階翻轉\增強\壓縮\伽馬變化

基本思想:基本原理參考OpenCV手冊，此處隻記錄一下如何使用；

#include<opencv2/opencv.hpp>
#include<iostream>
#include<vector>

using namespace std;
using namespace cv;


int main() {

    Mat img = imread("/home/ubuntu/Downloads/a.jpeg");
    cout << img.cols << "   " << img.rows << endl;
    Mat result;
    cvtColor(img, result, CV_BGR2GRAY);
    cout << result.channels() << endl;
    imwrite("gray.jpg",result);
    Mat gray0=result.clone();
    for (int i = 0; i < gray0.rows; i++) {
        for (int j = 0; j < gray0.cols; j++) {
            gray0.ptr<uchar>(i, j)[0] = 255 - gray0.ptr<uchar>(i, j)[0];
        }
    }
    imwrite("subtract.jpg", gray0);
    //減法操作　似乎　相差幀的背景變化很少的時候　有用

    double xmin;
    double xmax;
    Mat gray1=result.clone();
    minMaxLoc(gray1,&xmin,&xmax,0,0);
    //将原來的空間的像素點拉伸到０－255空間中，　使用的比例計算（z-0）/(灰階像素－ｘmin)=(255-0)/(xmax-xmin)
    for (int i = 0; i < gray1.rows; i++) {
        for (int j = 0; j < gray1.cols; j++) {

            gray1.ptr<uchar>(i, j)[0]=(255-0)/(xmax-xmin)*(gray1.ptr<uchar>(i, j)[0]-xmin);

        }
    }
    imwrite("explosion.jpg",gray1);


    // 像素壓縮在 [50:150]區間範圍内
   Mat gray2=result.clone();
    minMaxLoc(gray2,&xmin,&xmax,0,0);
    //将原來的空間的像素點壓縮在５０－１５０空間中，　
    for (int i = 0; i < gray2.rows; i++) {
        for (int j = 0; j < gray2.cols; j++) {

            gray2.ptr<uchar>(i, j)[0]=(150-50)/(xmax-xmin)*(gray2.ptr<uchar>(i, j)[0]-xmin);

        }
    }
    imwrite("rar.jpg",gray2);

    // 像素壓縮在 [50:150]區間範圍内
    Mat gray3=result.clone();

    for (int i = 0; i < gray2.rows; i++) {
        for (int j = 0; j < gray2.cols; j++) {

            gray3.ptr<uchar>(i, j)[0]=pow((gray3.ptr<uchar>(i, j)[0])/255.0,5.0)*255;

        }
    }
    imshow("gray.jpg",result);
    imshow("gama.jpg",gray3);

    waitKey(0);
    return 0;
}