PImage[] imgs = new PImage[4]; // loaded images
PImage img;                    // current image
int curImg = 0;                // current image

void setup()
{
  size(400,600);
  
  for(int i = 0; i < imgs.length; i ++) imgs[i] = loadImage("img-"+(i+1)+".jpg");
  img = imgs[curImg];
}

// makes a copy of the current image
PImage makeCopy(PImage src) {
  PImage ret = new PImage(src.width,src.height); // make a image
  ret.copy(src,0,0,src.width,src.height,0,0,ret.width,ret.height); //copy pixels
  return ret;
}

void draw()
{
  // compute the filtered images
  PImage f1 = makeCopy(img); f1.filter(THRESHOLD,map(mouseX,0,width,0,1));
  PImage f2 = makeCopy(img); f2.filter(POSTERIZE,map(mouseX,0,width,100,2));
  PImage f3 = makeCopy(img); f3.filter(BLUR,map(mouseX,0,width,0,10));
  
  // draw them
  background(0);  
  image(img,0,0);
  image(f1,0,height/2);
  image(f2,width/2,0);
  image(f3,width/2,height/2);
}

void keyPressed()
{
  if(key == ' ') {
    curImg = (curImg+1)%imgs.length;
    img = imgs[curImg];
  }
}

// START NO NOTES
// code used to capture screenshots
void keyReleased() {
  if(key == '`' && !online) save("sketch.png");
}