And there are Imager ppms that work on windows. And you can resize like this:

# Convert image from data in scalar
my $img = Imager->new;
$img->read(data=>$PixData, type=>'jpeg')
           or die "Cannot read: ", $img->errstr;

my $thumb = $img->scale(scalefactor=>.3);

$thumb->write(file=>"$0-t.jpg", type=>'jpeg')
           or die "Cannot write: ",$img->errstr;
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Instead of 'data=>', you can use 'file=>' to read from a file.