class DRAWGENERATIVE extends Shader {

  // choose channel  
  int channel = HUE; 

  // run, after 30 iterations result will be saved automatically
  // or press SPACE


  // channels to work with
  final static int RED = 0;
  final static int GREEN = 1;
  final static int BLUE = 2;
  final static int HUE = 3;
  final static int SATURATION = 4;
  final static int BRIGHTNESS = 5;
  final static int NRED = 6;
  final static int NGREEN = 7;
  final static int NBLUE = 8;
  final static int NHUE = 9;
  final static int NSATURATION = 10;
  final static int NBRIGHTNESS = 11;

  int n=2000;
  float [] cx=new float[n];
  float [] cy=new float[n];

  int len;

  // working buffer
  PGraphics buffer; 


  int tick = 0;


  DRAWGENERATIVE() {
    name = "fxDrawGenerative";
    buffer = createGraphics(renderer.width, renderer.height);
    buffer.noFill();
    buffer.beginDraw();
    buffer.strokeWeight(0.3);
    //buffer.background(0); //ENABLE THIS TO DRAW FROM BLANK
    buffer.endDraw();
    rw = renderer.width;
    len = (renderer.width<renderer.height?renderer.width:renderer.height)/6;

    for (int i=0; i<n; i++) {
      cx[i]=random(renderer.width);
      cy[i]=random(renderer.height);
    }
  }
  

  int rw;
  void apply() {
    if (rw != renderer.width) {
      rw = renderer.width;
      PGraphics save = createGraphics(renderer.width, renderer.height);
      save.beginDraw();
      save.image(buffer, 0, 0, save.width, save.height);
      save.endDraw();
      buffer.setSize(renderer.width, renderer.height);
      buffer.beginDraw();
      buffer.image(save,0,0,buffer.width,buffer.height);
      buffer.endDraw();
    }
    buffer.beginDraw();
    for (int i=1; i<n; i++) {
      color c = renderer.get((int)cx[i], (int)cy[i]);
      buffer.stroke(c);
      buffer.point(cx[i], cy[i]);
      // you can choose channels: red(c), blue(c), green(c), hue(c), saturation(c) or brightness(c)
      cy[i]+=sin(map(getChannel(c), 0, 255, 0, TWO_PI));
      cx[i]+=cos(map(getChannel(c), 0, 255, 0, TWO_PI));
    }
    if (frameCount>len) {
      frameCount=0;
      println("iteration: " + tick++);
      for (int i=0; i<n; i++) {
        cx[i]=random(renderer.width);
        cy[i]=random(renderer.height);
      }
    }
    buffer.endDraw();
    renderer.beginDraw();
    renderer.image(buffer, 0, 0, renderer.width, renderer.height);
    renderer.endDraw();
  }


  float getChannel(color c) {
    int ch = channel>5?channel-6:channel;
    float cc;

    switch(ch) {
    case RED: 
      cc = red(c); 
      break;
    case GREEN: 
      cc = green(c); 
      break;
    case BLUE: 
      cc = blue(c); 
      break;
    case HUE: 
      cc = hue(c); 
      break;
    case SATURATION: 
      cc = saturation(c); 
      break;
    default: 
      cc= brightness(c); 
      break;
    }

    return channel>5?255-cc:cc;
  }
}