use v5.36;
use PDL;
use PDL::Image2D;
my $w=4;
my $h=5;
my $m=sequence(10,10); # or any other matrix
say $m->conv2d(ones($w,$h))->slice([floor(($w-1)/2),floor(-($w+1)/2)],
    [floor(($h-1)/2),floor(-($h+1)/2)]);