#include <opencv2/core.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/imgcodecs.hpp>
#include <opencv2/imgproc.hpp>

#include <iostream>

using namespace cv;

int main(int argc, char **argv) {
  if (argc != 2) {
    std::cerr << "Please input an image file path as the only arg."
              << std::endl;
    return -1;
  }

  const char *filename = argv[1];
  Mat I = imread(samples::findFile(filename), IMREAD_GRAYSCALE);
  if (I.empty()) {
    std::cout << "Error opening image" << std::endl;
    return EXIT_FAILURE;
  }
  Mat padded; // expand input image to optimal size
  int m = getOptimalDFTSize(I.rows);
  int n = getOptimalDFTSize(I.cols); // on the border add zero values
  copyMakeBorder(I, padded, 0, m - I.rows, 0, n - I.cols, BORDER_CONSTANT,
                 Scalar::all(0));
  Mat planes[] = {Mat_<float>(padded), Mat::zeros(padded.size(), CV_32F)};
  Mat complexI;
  merge(planes, 2, complexI); // Add to the expanded another plane with zeros
  dft(complexI, complexI); // this way the result may fit in the source matrix
  // compute the magnitude and switch to logarithmic scale
  // => log(1 + sqrt(Re(DFT(I))^2 + Im(DFT(I))^2))
  split(complexI, planes); // planes[0] = Re(DFT(I), planes[1] = Im(DFT(I))
  magnitude(planes[0], planes[1], planes[0]); // planes[0] = magnitude
  Mat magI = planes[0];
  magI += Scalar::all(1); // switch to logarithmic scale
  log(magI, magI);
  // crop the spectrum, if it has an odd number of rows or columns
  magI = magI(Rect(0, 0, magI.cols & -2, magI.rows & -2));
  // rearrange the quadrants of Fourier image  so that the origin is at the
  // image center
  int cx = magI.cols / 2;
  int cy = magI.rows / 2;
  Mat q0(magI, Rect(0, 0, cx, cy));   // Top-Left - Create a ROI per quadrant
  Mat q1(magI, Rect(cx, 0, cx, cy));  // Top-Right
  Mat q2(magI, Rect(0, cy, cx, cy));  // Bottom-Left
  Mat q3(magI, Rect(cx, cy, cx, cy)); // Bottom-Right
  Mat tmp; // swap quadrants (Top-Left with Bottom-Right)
  q0.copyTo(tmp);
  q3.copyTo(q0);
  tmp.copyTo(q3);
  q1.copyTo(tmp); // swap quadrant (Top-Right with Bottom-Left)
  q2.copyTo(q1);
  tmp.copyTo(q2);
  normalize(magI, magI, 0, 1,
            NORM_MINMAX); // Transform the matrix with float values into a
                          // viewable image form (float between values 0 and 1).
  imshow("Input Image", I); // Show the result
  imshow("spectrum magnitude", magI);
  waitKey();
  return EXIT_SUCCESS;
}