#!/usr/bin/perl

=head1 DESCRIPTION

This program demonstrates how to load a large GIF animation
in Perl Tk without having to wait forever. Thank you vr!

Question: Why is Tk::Animation so slow?
https://www.perlmonks.org/index.pl?node_id=11110499

Answer: Apparently...something horribly unoptimized happens inside Tk.
https://www.perlmonks.org/index.pl?node_id=11110521
https://www.perlmonks.org/index.pl?node_id=11110545

=head1 SYNOPSIS

On first run it downloads and saves a 28MB animated GIF
from archive.org to the current directory. Subsequent runs
use the local image. The image is Comet ISON grazing the sun
taken with the Large Angle Coronagraph on NASA/ESA's Solar
Heliospheric Observatory.

=cut

use autodie;
use strict;
use warnings;

use HTTP::Tiny;
use MIME::Base64;
use Time::HiRes 'time';

use Imager ':handy';
use Tk;
use Tk::Animation;
use Tk::Photo;

my $file = 'ghost_anim.gif';
my $path;

if (-e $file) {
  print "Loading image $file \n";
  open my $fh, '<', $file;
  $path = join '', <$fh>
}
else {
  my $http = 'http://web.archive.org/web/20131202114602if_/'.
  'http://science.nasa.gov/media/medialibrary/2013/12/01/'.
  $file;
  
  print "Downloading image $http \n";
  
  $path = HTTP::Tiny->new->get($http)->{content};
  die 'Download failed!' unless $path;
  
  open my $fh, '>', $file;
  $fh->binmode;
  print $fh $path
}
my $size = length $path;

my $mw = MainWindow->new;
$mw->configure(-title => 'Comet ISON via SOHO LASCO C3');
my $top = $mw->Frame->pack;

my $backdrop;
my $start = time;

my @frames = map {
  if ($backdrop) { # not 1st?
    my $mask      = $_->copy;
    my @mask_plt  = map NC(255, 255, 255), $_->getcolors;
    my $trans_idx = $_->tags(name => 'gif_trans_index');
    my $left      = $_->tags(name => 'gif_left');
    my $top       = $_->tags(name => 'gif_top');

    $mask_plt[$trans_idx] = NC(0, 0, 0) 
    if defined $trans_idx;
    
    $mask->setcolors(colors => \@mask_plt);
    
    $backdrop->compose(
      src  => $_,
      mask => $mask, 
      tx   => $left,
      ty   => $top
    )
  }
  else {
    $backdrop = $_->to_rgb8
  }
  $backdrop->write(data => \my $data, type => 'bmp');
  $mw->Photo(-data => encode_base64($data))
  
} Imager->read_multi(data => $path);

my $image = $mw->Animation;
$image->add_frame(@frames);

print join ' ',
"\nImager & Tk::Animation took", time - $start,
"seconds for $size bytes \n";

$top->Label(-image => $image)->pack;
$image->start_animation;

MainLoop
[download]