Transicao

PImage imgOriginal, img;

int posy = 0;

void setup(){

  size(320,240);
  imgOriginal = loadImage("original.png");
  img = loadImage("img.png");
}

void draw(){

  image (imgOriginal, 0, 0);
  image (img, 0, posy);
  for (int i=0; i<240; i++);
    posy++;

   }