#!/usr/bin/perl -wT
use strict;
use POSIX;

$ENV{PATH} = '/usr/bin';

my $minW = 320;
my $maxW = 2000;
my @densities = (0.5, 1.0, 2.0);

my $maxOver = 1.3;

my $images = [];

my $width = $maxW * $densities[$#densities];
while ($width > $minW * $densities[0] * $maxOver) {
    push(@$images, POSIX::ceil($width));
    $width /= $maxOver;
}

foreach my $w (@$images) {
    system("convert original.jpeg -resize $w $w.jpeg") unless -f "$w.jpeg";
    foreach my $d (reverse @densities) {
        my $nw = int($w / $d);
        next if $nw > $maxW;
        next if $nw < $minW;
        print "$w.jpeg ${nw}w ${d}x,\n";
    }
}