# preload the derivative cache
    if (not defined $opt{'no-cache'} and $row->{customer_status} ne 'suspended' and $gallery_locked ne 'true') {
        build_cache('medium');
        build_cache('thumb');
        build_cache('square');
    }
    
sub build_cache {
    my ($type) = @_;

    our ($ua, $base_url);

    my $response = $ua->post(
        $base_url.'/ws.php?format=json',
        {
            method => 'pwg.getMissingDerivatives',
            types => $type,
            max_urls => 100_000
        }
    );

    my $result = from_json($response->content)->{result};

    if (ref($result) ne 'HASH' or not defined $result->{urls}) {
        return;
    }

    my @urls = @{ $result->{urls} };
    print scalar(@urls).' '.$type.' images to build'."\n";

    use Time::HiRes qw/gettimeofday tv_interval/;

    my $i = 0;

    foreach my $url (@urls) {
        my $t1 = [gettimeofday];

        printf(
            '[%s] photo %s %0'.length(scalar(@urls)).'u/%u generation in progress... ',
            $url, # $row->{username},
            $type,
            ++$i,
            scalar(@urls)
        );

        $ua->get($url.'&ajaxload=true');

        my $elapsed = tv_interval($t1);
        printf('%u ms', $elapsed * 1000);
        print "\n";
    }
}