#! perl -slw
use strict;
use Tk;
use Tk::PNG;
use GD::Graph;
use GD::Graph::bars;
use MIME::Base64 qw[ encode_base64 ];

my $data = [
   [qw/1st 2nd 3rd 4th 5th 6th 7th 8th 9th/],
   [qw/  1   2   5   6   3 1.5   1   3   4/],
];

my $graph = GD::Graph::bars->new(400, 300);
$graph->set(
   x_label        => 'X Label',
   y_label        => 'Y label',
   title          => 'Some simple graph',
   y_max_value    => 8,
   y_tick_number  => 8,
   y_label_skip   => 2
) or die $!;

my $gd = $graph->plot($data) or die $!;

my $mw = MainWindow->new;
my $png = $mw->Photo(
#    -data => encode_base64( $gd->png ),
    -data =>  $gd->png,
    -format => 'png'
);

my $btn = $mw->Button( -text => 'doit', -command => sub{
    $data->[ 1 ] = [ map{ rand 5 } 1 .. 9 ];
    undef $graph;
    $graph = GD::Graph::bars->new(400, 300);
    $graph->set(
       x_label        => 'X Label',
       y_label        => 'Y label',
       title          => 'Some simple graph',
       y_max_value    => 8,
       y_tick_number  => 8,
       y_label_skip   => 2
    ) or die $!;

    my $gd = $graph->plot($data) or die $!;
    $png->blank;
    $png->configure(
#        -data  => encode_base64( $gd->png ),
        -data  => $gd->png,
        -format => 'png'
    );
    $mw->update;
} )->pack;

$mw->Label(-image => $png)->pack;

$mw->repeat( 1000, sub{ $btn->invoke; $png->update } );
MainLoop;

__END__
couldn't recognize image data at c:/Perl/site/lib/Tk/Image.pm line 21.