#!/usr/bin/perl 
use strict;
use warnings;
use v5.12;
use File::Temp qw/ tempdir /;
use Graphics::Magick;
use Math::Round qw(:all);
my $p = new Graphics::Magick;
$p->Read("Felis_silvestris_silvestris_small.png");
#$p->Resize('x600');
my ($width, $height) = $p->Get('width', 'height');
my $center = $height;
my $result = new Graphics::Magick;
$result->Set(size=>"${width}x${height}");
$result->Read();
$result->Set('quality', 100);
my $dir = tempdir(CLEANUP => 1);
my $chop = 16; # 1 MCU normally
my $vertical = 0;
for my $n (0..($vertical?$height:$width)) {
        next if $n%$chop; 
        my $current = $p->Clone();
        $current->Crop(width => $vertical?$width:$chop, height => $vertical?$chop:$height, x => $vertical?0:$n, y=>$vertical?$n:0);
		my $quality =  round_even(100*abs(($n+6*$chop)**4/$center**4));
		say $quality;
        $current->Set('quality' => $quality);
        my $filename = sprintf "%s/%05d.jpg", $dir, $n;
        $current->Write($filename);
        my $m = new Graphics::Magick;
        $m->Read($filename);
        $result->Composite( image => $m, x => $vertical?0:$n, y => $vertical?$n:0);
}
$result->Write('Felis_silvestris_silvestris_small_gradual_decrease_of_quality.png');