invertImage.cpp

Mat invertImage(Mat image) {
    Vec3b p;

    for (int i = 0; i < image.rows; ++i)
    {
        for (int j = 0; j < image.cols; ++j)
        {
            p = image.at<Vec3b>(i, j);
            image.at<Vec3b>(i, j)[0] = 255 - p[0];
            image.at<Vec3b>(i, j)[1] = 255 - p[1];
            image.at<Vec3b>(i, j)[2] = 255 - p[2];
        }
    }

    return image;
}