// defaults to .png
static File saveImageWithCounter(File dir, S baseName, BufferedImage img) {
  if (img == null || dir == null) null;
  
  if (!isImageFileName(baseName)) baseName += ".png";
  File f = makeFileNameUnique_beforeExtension_startWith1_noDot(newFile(dir, baseName));
  saveImage(f, img);
  infoBox("Saved image " + appendBracketed(img.getWidth(null) + "*" + img.getHeight(null)) + ": " + fileInfo(f));
  ret f;
}