import controlP5.*;    

PImage img;

ControlP5 controlP5;

static float imgw = 800;
static float imgh = 600;

PImage diffImg;

static int MAXPOINTS = 10;

PVector [] mypoints;

float center=30.0;
float width=30.0;
int count=0;

void setup() {
  size(1600, 800);
  img = loadImage("urs_firscher_060_push.jpg"); // Load demo image
  background(255);

  controlP5 = new ControlP5(this);

  controlP5.addSlider("center")
    .setPosition(10, imgh+20)
      .setRange(0, 255)
        .setValue(30.0)
          .setCaptionLabel("center");
  controlP5.addSlider("width")
    .setPosition(10, imgh+50)
      .setRange(0, 255)
        .setValue(30.0)
          .setCaptionLabel("width");

  mypoints = new PVector[MAXPOINTS];
  diffImg = createImage((int)imgw, (int)imgh, RGB);
 
}

void draw() {

  createStrokeGroup();
  drawStrokeGroup();
  
  count++;
  if(count==10) {
    calcDiffImage();
    count=0;
  }
}

PVector findPoint() {
  return findPoint(0, 255);
};

PVector findPoint(float center, float width) {
  color c;
  float ix, iy;
  float x, y;
  float bright;
  boolean done=false;
  // weighted sample towards darker pixels
  do {
    ix=random(0, img.width);
    iy=random(0, img.height);
    c = img.get((int)ix, (int)iy);
    bright = brightness(c);
    if ((bright>center-width/2) && (bright<=center+width/2) && (random (width)<(float)width/2)) done=true;
  } 
  while ( !done);
  //println(ix);
  //println(iy);
  return new PVector(ix, iy);
}

void createStrokeGroup() {
  for (int i=0;i<MAXPOINTS;i++) {
    PVector result = findPoint(center, width);
    println(result.x);
    println(result.y);
    mypoints[i] = new PVector(result.x, result.y);
  }
}

void drawStrokeGroup() {
  for (int i=0;i<MAXPOINTS;i++) {
    color c = img.get((int)mypoints[i].x, (int)mypoints[i].y);
    fill(c);
    stroke(c);
    strokeWeight(random(2, 5));
    float x=mypoints[i].x*(float)imgw/(float)img.width;
    float y=mypoints[i].y*(float)imgh/(float)img.height;

    line(10+x, 10+y, 10+x+random(-10, 10), 10+y+random(-10, 10));
  }
}

void calcDiffImage() {
  color cA, cB,colordiff;
  float diff;
  for(int x=0;x<imgw;x++)
    for(int y=0;y<imgh;y++) {
      int ix,iy;
      
      ix = (int)(x*(float)img.width/(float)imgw);
      iy = (int)(y*(float)img.height/(float)imgh);
      colordiff = img.get(ix, iy)-get(x,y);
      diff = mag(red(colordiff),green(colordiff),blue(colordiff));
      
//      diffImg.set(x,y,colordiff);
      diffImg.set(x,y, (int)color(diff));
    }
  image(diffImg, imgw, 0);
}