PImage up;
PImage down;
PImage left;
PImage right;
PImage current;

// position
float x, y;

void setup() {
  size(200, 200);
  up = loadImage("arrow_up.png");
  down = loadImage("arrow_down.png");
  left = loadImage("arrow_left.png");
  right = loadImage("arrow_right.png");
  current = up;

  x = width/2;
  y = height/2;
}

void draw() {
  background(240);

  image(current, x, y); //, 64, 64);

  if (keyPressed) {
    if (key == CODED) {
      if (keyCode == UP) {
        current = up;
        y = y - 2;
      }
      if (keyCode == DOWN) {
        current = down;
        y = y + 2;
      }
      if (keyCode == RIGHT) {
        current = right;
        x = x + 2;
      }
      if (keyCode == LEFT) {
        current = left;
        x = x - 2;
      }  
    }  
  }
}