Get QR code data from a png scalar

This example program demonstrates extracting the QR code data from a QR code generated with Image::PNG::QRCode using Image::PNG::Libpng and then writing it out again using Cairo. See also LeMoDa.net's Perl Cairo tutorial.

#!/home/ben/software/install/bin/perl
use warnings;
use strict;
use utf8;
use FindBin '$Bin';

use Image::PNG::QRCode 'qrpng';
use Image::PNG::Libpng ':all';
use Cairo;

# Test getting the data from a QR code using Image::PNG::QRCode and
# Image::PNG::Libpng.

my $text = 'qrpng';
my $qrpng = qrpng (text => $text, scale => 1);
my $png = read_from_scalar ($qrpng);
my $rows = $png->get_rows ();
my $header = $png->get_IHDR ();
my $width = $header->{width};
my $height = $header->{height};
my @image;
for my $row (@$rows) {
    my $bits = unpack ("B$width", $row);
    push @image, $bits;
}
my $scale = 5;
my $surface = Cairo::ImageSurface->create ('argb32', $width * $scale, $height * $scale);
my $cr = Cairo::Context->create ($surface);
my $y = 0;
my $x = 0;
for my $row (@image) {
    for my $column (split //, $row) {
        if ($column) {
            $cr->set_source_rgb (1, 1, 1);
        }
        else {
            $cr->set_source_rgb (0, 0, 0);
        }
        $cr->rectangle ($x * $scale, $y * $scale, ($x + 1) * $scale, ($y + 1) * $scale);
        $cr->fill ();
        $x++;
    }
    $x = 0;
    $y++;
}
$surface->write_to_png ('qr.png');

(download)

The output looks like this: