At a given point of some processing I have a list of polygons (an array of arrays of x y coordinates).
I want to generate a .png image of the filled polygons. There are a few modules I can use, GD, Imager, ImageMagick, PDL, maybe more.
I've tried GD vs Imager as in:

use GD;
my $img = new GD::Image ($width, $height);
my $black = $img->colorAllocate (0,0,0);
my $white = $img->colorAllocate (255,255,255);
map {
  my $polygon = GD::Polygon->new;
  map { $polygon->addPt (round ($_->[0] * $scale - $minx),
                 round ($maxy - $_->[1] * $scale)); } @{$_};
  $img->filledPolygon ($polygon,$white);
} @polygons;
print $img->png ();

[download]
use Imager;
my $img = Imager->new (xsize=>$width, ysize=>$height,
                       channels=>1, bits=>8);
map {
  my @polygon = ();
  map { push (@polygon,
          [round ($_->[0] * $scale - $minx),
           round ($maxy - $_->[1] * $scale)]) } @{$_};
  $img->polygon (points=>\@polygon, color=>'white');
} @polygons;
$img->write (fd => fileno(STDOUT), type=>'png');

[download]

For a sample set size of 12690 polygons, generating a 7917x38558 image, the GD approach runs in about 7 seconds, the Imager approach runs in about 209 seconds, a very large difference.

Cursory inspection with top reveals very similar memory and CPU requirements

What am I overlooking, or is this the way it is?

In reply to Filling polygons: Imager vs GD by HASM

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