use Imager;
use Imager::Filter::Autocrop;

my $imgdata = undef;
open(IN, '<', 'example.jpg');
binmode(IN);
{ local $/ = undef; $imgdata = <IN> }
close(IN);

my $img = Imager->new();
$img->register_reader(
        type => 'scalar',
        single => sub {
                my ($im, $io, %hsh) = @_;
                $im->{IMG} = $io;
                return $im
        },
) or die "register_reader: ".$img->errstr();

$img->read(type=>'scalar', file=>$imgdata) or die "read: ".$img->errstr();
$img->autocrop(fuzz=>20) or die "autocrop: ".$img->errstr();
$img->write(file=>'out.jpg') or die "writing: ".$img->errstr();