// image static
PImage colorbars;
int x;

void setup(){
  size(320,240);
  colorbars = loadImage("colorbars.jpg");
}

void draw(){
  //image(colorbars, 0,0);
  loadPixels();
  for(int p=0; p<width*height; p++){
    x = p*2;
    if(x >= width*height){
      x = x - width*height;
    }
    pixels[p] = colorbars.pixels[x];
  }
  updatePixels();
}