my ($w,$h)=$img->Get('width','height');
my $want_aspect=3/2;
my $is_aspect=$w/$h;

if($want_aspect-$is_aspect > 0)
{ $w=int((1/$want_aspect)*$h); }
else
{ $h=int($want_aspect*$w); }

$img->Crop(width=>$w, height=>$h, gravity=>'Center');