use strict;
use warnings;
use Imager;
use MCE;

# based on original http://www.alfrog.com/mandel.html
# karlgoethebier: code refactor
# marioroy: parallelization

my $width      = 1280;
my $height     = 1024;
my $iterations = 20;
my @palette;
my $image;

my $mce = MCE->new(
   use_threads => 0,  # MCE defaults to threads on windows
   max_workers => 'auto',
   chunk_size  => 8,

   gather => sub {
      my ( $x, $y, $color );
      while ( ($x, $y, $color) = splice(@_, 0, 3) ) {
         $image->setpixel( x => $x, y => $y, color => $palette[$color] );
      }
   },

   user_func => sub {
      my ( $mce, $chunk_ref, $chunk_id ) = @_;
      my ( $re_c, $im_c, $re_z, $im_z, $color, $temp );
      my ( @set_data );

      for my $x ( $chunk_ref->[0] .. $chunk_ref->[1] ) {
         for my $y ( 0 .. $height - 1 ) {
            $re_c = ( $x - 3 * $width / 4 ) / ( $width / 3 );
            $im_c = ( $y - $height / 2 ) / ( $width / 3 );
            $re_z = $im_z = $color = 0;

            while ( 1 ) {
               $temp = $re_z;
               $re_z = $re_z * $re_z - $im_z * $im_z + $re_c;
               $im_z = 2 * $temp * $im_z + $im_c;
               ++$color;

               last if $re_z * $re_z + $im_z * $im_z > 4;

               if ( $color == $iterations ) {
                  $color = 0;
                  last;
               }
            }

            push @set_data, $x, $y, $color;
         }
      }

      MCE->gather( @set_data );
   }
);

# spawn MCE workers
$mce->spawn;

# init image and color palette
$image = Imager->new( xsize => $width, ysize => $height );
push @palette, Imager::Color->new( 0, 0, 0 ); # black

for ( 1 .. $iterations ) {
   my ( $r, $g, $b ) = map { int rand 255 } 1 .. 3;
   push @palette, Imager::Color->new( $r, $g, $b );
}

# compute mandelbrot
$mce->process({ bounds_only => 1, sequence => [ 0, $width - 1 ] });
$mce->shutdown;

# save image
my $file = qq(mandelbrot.png);
$image->write( file => $file );