This works for me. I have used Image::PNG::Libpng. Somehow last night, in the dark, it looked scary but in the light of day it turns out to be quite adorable. And fast too.

use Image::PNG::Libpng ':all';
use Image::PNG::Const ':all';

my $W = 500;
my $H = 500;
my $compression_level = 9;
#################################

my %ihdr = (
    width => $W,
    height => $H,
    bit_depth => 8,
    # one of: PNG_COLOR_TYPE_GRAY, PNG_COLOR_TYPE_GRAY_ALPHA, PNG_COLO
+R_TYPE_PALETTE, PNG_COLOR_TYPE_RGB, PNG_COLOR_TYPE_RGB_ALPHA.
    color_type => PNG_COLOR_TYPE_RGB,
);

my @rows;
for my $y (0..$H-1){
        # each row is a binary string packing $W (R,G,B) triplets (not
+ an array)
        # so we keep appending to this binary buffer (a string! but bi
+nary string ok,right?)
    my $col_bin_str = "";
    for my $x (0..$W-1){
        my $R = int(rand()*0x100);
        my $G = int(rand()*0x100);
        my $B = int(rand()*0x100);
        # test compression with this "compressable" content
#        my ($R, $G, $B) = (0xFF) x 3;
        # pack an R,G,B tripplet into 3 bytes, each an unsingned char
                # that would be different for different scheme (RGBA) 
+etc.
        $col_bin_str .= pack "CCC", $R, $G, $B;
    }
    push @rows, $col_bin_str;
}
my $png = create_writer('file.png');
$png->set_compression_level($compression_level);
$png->set_IHDR(\%ihdr);
$png->set_rows(\@rows);
$png->write_png();
[download]

bw, bliako