I have this very simple program here:

int frames = 81;
PImage[] images = new PImage[frames];

void setup() {
  size(640, 480);
  for (int i = 0; i < images.length; i++) {
    String imageName = nf(i,4) + ".jpg";
    images[i] = loadImage(imageName);
  }
  frameRate(24);
}

void draw(){
  float x = random(0, 81);
  int currentFrame = int(x);
  image(images[currentFrame], 0, 0);
}

When I export it as an application and run it (I'm using Linux) I don't get the full screen size 640X480, but a cropped image, something closer to 100x100.  It runs fine from within Processing. 

New at this, so maybe missing something obvious.  Any help is greatly appreciated.
Thanks.