image.cpp

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#include "sigpack.h"
using namespace arma;
using namespace sp;

int main()
{
  PNM ppm; // Portable Pixel Map

  int R = 120, C = 160;
  mat x(R, C);
  cx_mat X(R, C);
  mat mag(R, C);
  FFTW ss(R, C, FFTW_ESTIMATE);

  gplot gp0, gp1;
  gp0.window("Image", 10, 10, 2 * C + 80, 2 * R + 50);
  gp1.window("FFT Blue channel", 640, 10, 2 * C + 80 + 50, 2 * R + 50);

  // Generate test image
  cube x3(R, C, 3, fill::randu);
  x3 *= 100;
  x3.slice(0).submat(span(20, 51), span(20, 51)) =
      250 * ones(32, 32); // Red box
  x3.slice(1).submat(span(80, 111), span(70, 101)) =
      250 * ones(32, 32); // Green box
  x3.slice(2).submat(span(20, 51), span(110, 141)) =
      250 * ones(32, 32); // Blue box

  // Write to file
  ppm.write("test.ppm", ppm.PPM_B, x3, "Test picture");

  // Do FFT of blue channel
  x   = x3.slice(2);
  X   = ss.fft2(x);
  mag = 20 * log10(abs(fftshift(X)));

  // Plot
  gp0.set_term("qt");
  gp0.image(x3);
  gp1.set_term("qt");
  gp1.send2gp("set palette grey");
  gp1.image(mag);

  return 0;
}