var mouse_down = false;

var max_amp = -4;

var min_amp = -5;

var zoom_by = 4;

var zoom_slider;

var ellipse_slider;

​

function setup() {

  createCanvas(256, 512);

  background(220);

  pixelDensity(1);

  background(0);

  stroke(255);

  line(0, height / 2 + 1, width, height / 2 + 1);

  createDiv("Zoom:");

  zoom_slider = createSlider(1, 5, 1, 0.1);

  createDiv("Pen size:");

  ellipse_slider = createSlider(1, 20, 10, 0.1);

}

​

function draw() {

  noStroke();

  if (mouse_down) {

    ellipse(mouseX, mouseY, ellipse_slider.value(), ellipse_slider.value());

  }

  stroke(255);

  line(0,height/2+1,width,height/2+1);

​

}

​

function mousePressed() {

  mouse_down = true;

  //

​

  //  updateAmp();

}

​

function mouseClicked() {

  mouse_down = false;

  updateAmp();

}

​

function updateAmp() {

  loadPixels();

  amp = [];

  for (i = 0; i < width; i++) {

    var tmp = [];

    for (j = 0; j < height / 2; j++) {

      tmp.push([pixels[4 * (j + i * width)] / 255.0, 0.0]);

    }

    amp.push(tmp);

  }

​

  const F2d0 = fft2dr(amp);

​

  for (i = 0; i < width; i++) {

    for (j = 0; j < height / 2; j++) {

      var im_intensity =

        F2d0[(i + width / 2) % width][(j + height / 4) % (height / 2)][0] ** 2 +

        F2d0[(i + width / 2) % width][(j + height / 4) % (height / 2)][1] ** 2;

      min_amp = 0.0;

      max_amp = max(max_amp, sqrt(im_intensity));

    }

  }

​

  for (i = 0; i < width; i++) {

    for (j = 0; j < height / 2; j++) {

      var im_intensity =

        F2d0[(i + width / 2) % width][(j + height / 4) % (height / 2)][0] ** 2 +

        F2d0[(i + width / 2) % width][(j + height / 4) % (height / 2)][1] ** 2;

      //im_intensity = map(log(im_intensity+1e-7),min_amp,max_amp,0,255);

      im_intensity = map(sqrt(im_intensity), 0, max_amp, 0, 255);

      pixels[4 * (i + j * width + (width * height) / 2) + 0] = im_intensity;

      pixels[4 * (i + j * width + (width * height) / 2) + 1] = im_intensity;

      pixels[4 * (i + j * width + (width * height) / 2) + 2] = im_intensity;

    }

  }

​

  updatePixels();

  zoom_by = zoom_slider.value();

  image(

    get(

      width / 2 - width / 2 / zoom_by,

      height / 2 + height / 4 - height / 4 / zoom_by,

      width / zoom_by,

      height / 2 / zoom_by

    ),

    0,

    height / 2,

    width,

    height / 2

  );

}

​