1 files changed, 63 insertions, 0 deletions
diff --git a/store/works/life/digital-image-process-lab/DiscreteFourierTransform.cpp b/store/works/life/digital-image-process-lab/DiscreteFourierTransform.cpp
new file mode 100644
index 0000000..31108bb
--- /dev/null
+++ b/store/works/life/digital-image-process-lab/DiscreteFourierTransform.cpp
@@ -0,0 +1,63 @@
+#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;
+}