static byte[] rawImageFromImageServer(S md5) ctex {
  assertTrue(isMD5(md5));
  
  File dir = getCacheProgramDir("Images-by-MD5");
  File file = new File(dir, md5 + ".png");
  if (file.exists() && file.length() != 0) pcall {
    ret ImageIO.read(file);
  }

  byte[] data = loadBinaryPage(imageServerLink(md5));
  assertTrue(isPNG(data));
  ret data;
}