use strict;
use warnings;
use feature 'say';
use Time::HiRes 'time';
use Imager;

sub get_RGB_triplet { map { int rand 256 } 0 .. 2 }

{
    my $i = Imager-> new( xsize => 1000, ysize => 1000 );
    my $t = time;
    for my $y ( 0 .. 999 ) { 
        for my $x ( 0 .. 999 ) {
            my $c = Imager::Color-> new( get_RGB_triplet );
            $i-> setpixel( x => $x, y => $y, color => $c )
        }
    }
    say time - $t;
}
{
    my $i = Imager-> new( xsize => 1000, ysize => 1000 );
    my $t = time;
    for my $y ( 0 .. 999 ) { 
        my $packed_line = '';
        for my $x ( 0 .. 999 ) {
            $packed_line .= pack 'C3x', get_RGB_triplet;
        }
        $i-> setscanline( y => $y, pixels => $packed_line )
    }
    say time - $t;
}

__END__

5.78085088729858
0.599802017211914