opencv_example/example.cpp

#include <iostream>
#include <opencv2/opencv.hpp>
#include <sys/stat.h>
#include <string>
#include <vector>
#include <algorithm>

using namespace std;
using namespace cv;

std::vector<std::string> supportedExt = {
    "jpg", "JPG",
    "jpeg", "JPEG",
    "png", "PNG",
    "tif", "TIF",
    "tiff", "tiff"
};

inline bool in_array(const std::string &value, const std::vector<std::string> &array)
{
    return std::find(array.begin(), array.end(), value) != array.end();
}

inline bool file_exists (const std::string& name)
{
    struct stat buffer;   
    return (stat (name.c_str(), &buffer) == 0); 
}

inline bool is_image (const std::string& name)
{
    string ext = name.substr(name.find_last_of(".") + 1);
    return in_array(ext, supportedExt);
}
  
int main(int argc, char** argv)
{
    Mat image;
    Mat inverted;
    string input;
    
    if (argc == 2)
    {
        input = argv[1];
    } 
    else if (argc < 2) 
    {
        cerr << "Please provide one image." << endl;
        return -1;
    }
    else if (argc > 2)
    {
        cerr << "Please provide only one image." << endl;
        return -2;
    }

    if (!file_exists(input))
    {
        cerr << "File " << input << " does not exist." << endl;
        return -3;
    }

    if (!is_image(input))
    {
        cerr << "File " << input << " is not a valid image." << endl;
        return -4;
    }

    cout << "Using image " << input << "." << endl;

    image = imread(input);
    bitwise_not(image, inverted);
    imshow("Image", inverted);

    waitKey(0);

    destroyAllWindows(); 

    
  
    return 0;
}