I don't mess around on windows, but here is how it is done on linux. The code is probably close. There is Win::Photo for Win32 now......see Tk::WinPhoto for ActiveState. And see Tk Screen and Canvas Screenshots

If you want to try the postscript method on win32, here is how you do it.

#!/usr/bin/perl
use Tk;
#to change the background color, edit the ps file 
#  0.000 0.000 0.000 setrgbcolor AdjustColor 
#  fill 

$width = 800;
$height = 500;
my $main = MainWindow->new();
my $canvas = $main->Canvas( -width=>$width, -height=>$height, -backgro
+und=>"black");
$canvas->pack( -expand=>1,-fill=>'both');

&create;

$canvas->update;
$main->update;

$main->Button(
    -text    => "Save",
    -command => [sub {
         $canvas->update;
         my @capture=();
         my ($x0,$y0,$x1,$y1)=$canvas->bbox('all');
         @capture=('-x'=>$x0,'-y'=>$y0,-height=>$y1-$y0,-width=>$x1-$x
+0);
         $canvas -> postscript(-colormode=>'color',
                               -file=>$0.'.ps',
                               -rotate=>0,
                               -width=>800,
                               -height=>500,
                               @capture);

                              }

  ]  )->pack;


MainLoop;

sub create{
$canvas->createOval(100, 100, 600, 600,-fill=>'green')

}
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