static BufferedImage toBufferedImageOpt(O o) {
  if (o cast BufferedImage) ret o;
  if (o cast Image) ret copyImage(o);
  if (o cast MakesBufferedImage)
    ret o.getBufferedImage();
    
  ifdef toBufferedImageOpt_acceptFile
  if (o cast File)
    if (isImageFile(o))
      ret loadBufferedImageFile(o);
  endifdef
      
  S c = getClassName(o);
  
  // Keep this because it also works on imported objects
  if (eqOneOf(c, "main$BWImage", "main$RGBImage"))
    ret (BufferedImage) call(o, "getBufferedImage");
 
  ifdef PNGFile // Who uses this anymore?   
  if (eq(c, "main$PNGFile"))
    ret (BufferedImage) call(o, "getImage");
  endifdef
  
  ret null;
}