sub convert_special_characters($) {
	my $str = shift;

	$str =~ s/Ü/Ue/g;
	$str =~ s/Ä/Ae/g;
	$str =~ s/Ö/Oe/g;
	$str =~ s/\x{1E9E}/SZ/g; # U+1E9E
	$str =~ s/ß/sz/g;
	$str =~ s/ü/ue/g;
	$str =~ s/ä/ae/g;
	$str =~ s/ö/oe/g;

	return $str;
}

$content_img =~ s/(\[\[Image:)(.+)\/(.+)(\]\])/convert_special_characters($1.$2."_".$3.$4)/ge;