// angle is in degrees (clockwise, 0 is north, 360 is full rotation)
// uses white background
static BufferedImage rotateImageInSameSize(BufferedImage img, double angle) {
  int w = img.getWidth(), h = img.getHeight();
  BufferedImage canvas = newBufferedImage(w, h, Color.white);
  drawRotatedImageOnImage(img, canvas, 0, 0, angle, w/2, h/2);
  ret canvas;
}