[Processing] Rotate Image using a direction vector

rotateImage.pde

/**
 * Rotates an image around an angle
 * For this the direction vector dir will be used.
 * E.g. if you want to code something like Asteroids: 
 * A rocket, which is always pointing towards the direction it is flying to...
 * For details about atan2 see here: http://www.processing.org/reference/atan2_.html
 * 
 * keywords: atan, atan2, sin, cos, tan, vector, vektor, math, mathe, winkel, 
 * angle, rotation, processing.org, 360, TWO_PI, origin, ursprung, image, bild
 */

PImage img;
PVector pos = new PVector(30, 20);
PVector dir = new PVector(0.2, 0.1); 

void setup(){
  size(400, 400);
  imageMode(CENTER);
  img = loadImage("anImage.jpg");
}

void draw(){
  pushMatrix();
  translate(pos.x, pos.y);
  float angle = atan2(dir[i].y, dir[i].x) + PI/2;
  rotate(angle)
  image(img, 0 , 0);
  popMatrix();
}