/*
VORONOI DIAGRAM
 Jeff Thompson
 January 2012
 
 http://en.wikipedia.org/wiki/Voronoi_cell
 http://www.quora.com/Google-Chrome/How-does-Chrome-pick-the-color-for-the-stripes-on-the-Most-visited-page-thumbnails
 
 www.jeffreythompson.org
 */

int similarity = 50;
String filename = "StarryNight.jpg";
boolean saveIt = true;
PImage b;

void setup() {

  b = loadImage(filename);
  size(b.width, b.height);
  image(b, 0, 0);

  loadPixels();
  for (int i=0; i<pixels.length; i++) {

    // test neighbors
    color pxColor = pixels[i];

    if (i+1 % width != 0 && i+1 < pixels.length) {   // no wrapping!
      color L = pixels[i+1];
      if (testColor(L, pxColor)) {
        pixels[i+1] = pxColor;
      }
    }
    if (i-1 % width != 0  && i-1 >= 0) {              // no wrapping!
      color R = pixels[i-1];
      if (testColor(R, pxColor)) {
        pixels[i-1] = pxColor;
      }
    }
    if (i-width > 0) {
      color U = pixels[i-width];
      if (testColor(U, pxColor)) {
        pixels[i-width] = pxColor;
      }
    }
    if (i+width < pixels.length) {
      color D = pixels[i+width];
      if (testColor(D, pxColor)) {
        pixels[i+width] = pxColor;
      }
    }
  }
  updatePixels();

  if (saveIt) {
    save(similarity + "pxThres-" + filename);
  }
}

boolean testColor(color neighbor, color px) {

  float nR = red(neighbor);
  float nG = green(neighbor);
  float nB = blue(neighbor);

  float pxR = red(px);
  float pxG = green(px);
  float pxB = blue(px);

  if (abs(nR-pxR) <= similarity && abs(nG-pxG) <= similarity && abs(nB-pxB) <= similarity) {
    return true;
  }
  else {
    return false;
  }
}