void penSetOn(float x, float y, int c, float p, float r, PImage img) {

  float amount = r*r;

  for (int i=0;i<amount;i++) {
    float rd = random(TWO_PI);
    float rad = random(r);
    antiAliasSetOn(x+rad*cos(rd),y+rad*sin(rd),c,p,img);
  }

}

void antiAliasSetOn(float x, float y, int c, float p, PImage img) {
  int x0 = int(floor(x));
  int y0 = int(floor(y));
  int x1 = x0+1;
  int y1 = y0+1;

  float px1 = x-x0;
  float px0 = 1.0 - px1;
  float py1 = y-y0;
  float py0 = 1.0 - py1;

  float p00 = p * px0 * py0;
  float p01 = p * px0 * py1;
  float p10 = p * px1 * py0;
  float p11 = p * px1 * py1;

  softSetOn(x0,y0,c,p00,img);
  softSetOn(x0,y1,c,p01,img);
  softSetOn(x1,y0,c,p10,img);
  softSetOn(x1,y1,c,p11,img);
}

void softSetOn(int x, int y, int c0, float p0, PImage img) {

  int c1 = img.get(x,y);
  img.set(x,y,mixColor(c0,c1,p0));

}




int mixColor(int c0, int c1, float p0) {
  float p1 = 1.0 - p0;
  int r1 = c1>>16&0xFF;
  int g1 = c1>>8&0xFF;
  int b1 = c1&0xFF;
  int r0 = c0>>16&0xFF;
  int g0 = c0>>8&0xFF;
  int b0 = c0&0xFF;
  int r = int(p0*r0 + p1*r1);
  int g = int(p0*g0 + p1*g1);
  int b = int(p0*b0 + p1*b1);
  return (r<<16|g<<8|b);
}





void blurAt(int x, int y, int blurRadius, float blurLevel, PImage img) {
  float v = 1/(float)sq(1+blurRadius*2);
  float rr=0, gg=0, bb=0;
  for (int yo=-blurRadius;yo<=blurRadius;yo++) for (int xo=-blurRadius;xo<=blurRadius;xo++) {
    int xp = x+xo;
    int yp = y+yo;
    if (xp<0) xp=0;
    if (xp>=img.width) xp=img.width-1;
    if (yp<0) yp=0;
    if (yp>=img.height) yp=img.height-1;
    int c = img.get(xp,yp);
    rr += v*(c>>16&0xFF);
    gg += v*(c>>8&0xFF);
    bb += v*(c&0xFF);
  }
  int blurCol = int(rr)<<16|int(gg)<<8|int(bb);
  img.set(x,y,mixColor(blurCol,img.get(x,y),blurLevel));
}

void blur(PImage img) {
  PImage out = new PImage(img.width,img.height);
  for (int y=0;y<img.height;y++) for (int x=0;x<img.width;x++) {
    blurAt(x,y,1,1.0,img);
  }
}