#!/usr/bin/perl
use warnings;
use strict;
use Gtk2 -init;
use Time::HiRes qw( time );

my $time_start = time;

my $s = Gtk2::Gdk::Screen->get_default;
my $w = $s->get_root_window;

# pixbuf = $pixbuf->get_from_drawable ($src, $cmap, $src_x, $src_y,
#                                    $dest_x, $dest_y, $width, $height
+)

while (1){
my $p = Gtk2::Gdk::Pixbuf->get_from_drawable (
            $w, undef, 0, 0, 0, 0, $s->get_width, $s->get_height);

$p->save (time.'.png', "png");

}

my $time_end = time;
my $diff = $time_end - $time_start;
print "$diff\n";
[download]

If you have a command line bmp to png converter (or jpg etc. like this one), then you can do this quite easily without any of the complex installs:

#! perl -slw
use strict;
use Win32::GuiTest qw[FindWindowLike SetForegroundWindow SendKeys];
use Win32::Clipboard;

my $clip = Win32::Clipboard->new();

my @windows = FindWindowLike( 0, $ARGV[ 0 ] ); #Find it
die "Couldn't find window '$ARGV[ 0 ]" unless @windows;

for (@windows) {
    SetForegroundWindow( $_ ); # Make it active
    sleep 1;
    ## Send the Alt-print screen key sequence to copy
    ## the active window to the clipboard
    SendKeys("%{PRTSCR}");
}

my $fname = "$ARGV[ 0 ]-@{[ time() ]}";
print $fname;
if( my $bitmap = $clip->GetBitmap() ) {
    local $\;
    my $bmpfile = $fname . '.bmp';
    open my $bmp, '>', $bmpfile or die $!;
    binmode $bmp;
    print $bmp $bitmap;
    close $bmp;
    print "Bitmap written to $bmpfile\n";
    system "bmp2png $bmpfile";
    print "Converted to $fname.png";
}
else {
    die "Couldn't get bitmap from clipboard";
}
__END__
C:\test>screengrab Opera
Opera-1265829469
Bitmap written to Opera-1265829469.bmp
OK      Opera-12658294 ooooooooooooooooooooooooooooooooooooooooooooooo
+ooooo
Converted to Opera-1265829469.png
[download]

See the full example at the linked node but here is the shorter version.

    #!/usr/bin/perl -w

    use strict;
    use Win32::Clipboard;
    use Win32::GuiTest 'SendKeys';


    # Send "Print Screen" key to Windows.
    SendKeys('{PRTSCR}');


    # Get the image from the clipboard.
    my $screen = Win32::Clipboard::GetBitmap()
                 or die "No image captured: $!\n";


    # Print the image to a file.
    open    BITMAP, "> screen.bmp" or die "Couldn't open bitmap file: 
+$!\n";
    binmode BITMAP;
    print   BITMAP $screen;
    close   BITMAP;

    __END__
[download]

--
John.