my ($height, $width) = $image->Get ('height', 'width');
  my $portrait = $height > $width;
  my ($x, $y) = ! $portrait ? ($thumbX, $thumbY) : ($thumbY, $thumbX);
  my $scaleX = $x / $width;
  my $scaleY = $y / $height;
  my $scale = $scaleX < $scaleY ? $scaleX : $scaleY;

  $thumb->Resize (width=>$width * $scale+0.5, height=>$height * $scale+0.5);