05_modify_im_contrast_brightness.cpp

//
// Created by varora on 22/04/24.
//
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
#include <iostream>

// NOT "using namespace std;" here, to avoid collisions between the beta variable and std::beta in c++17
using std::cin;
using std::cout;
using std::endl;
using namespace cv;

int main( int argc, char** argv ) {
    CommandLineParser parser(argc, argv, "{@input | ims/sample.jpg | input image}");
    Mat image = imread(samples::findFile(parser.get<String>("@input")));
    if (image.empty()) {
        cout << "Could not open or find the image!\n" << endl;
        cout << "Usage: " << argv[0] << " <Input image>" << endl;
        return -1;
    }

    Mat new_image = Mat::zeros(image.size(), image.type());

    double alpha = 1.0; /*< Simple contrast control */
    int beta = 0; /*< Simple brightness control */

    cout << " Basic Linear Transforms " << endl;
    cout << "-------------------------" << endl;
    cout << "* Enter the alpha value [1.0-3.0]: ";
    cin >> alpha;
    cout << "* Enter the beta value [0-100]: ";
    cin >> beta;

    for (int y = 0; y < image.rows; y++) {
        for (int x = 0; x < image.cols; x++) {
            for (int c = 0; c < image.channels(); c++) {
                new_image.at<Vec3b>(y, x)[c] =
                        saturate_cast<uchar>(alpha * image.at<Vec3b>(y, x)[c] + beta);
            }
        }
    }

    imshow("Original Image", image);
    imshow("New Image", new_image);

    waitKey();
    return 0;
}