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Recall our circle bitmap from Figure 17-5 and how, with the addition of an inverted mask, we made the circle transparent. Using a timer event, we can make the bitmap cycle between solid and transparent so it flashes like a pulsar.
$mw->repeat(100 => sub {
$b->configure(-maskfile => $count++ % 2 ? undef : 'circle.msk');
});Some call this animation, crude as it may be.
Perl/Tk supplies an Animation widget in the standard distribution, designed to render a series of Photos, like frames in a movie film. It's also smart enough to handle GIF89 images that contain multiple frames per image. Here's a program that accepts a list of image filenames from the command line and animates them.
my $animate;
if (@ARGV) {
$animate = $mw->Animation;
foreach (@ARGV) {
$animate->add_frame($mw->Photo(-file => $_));
}
} else {
my $gif89 = Tk->findINC('anim.gif');
$animate = $mw->Animation(-format => 'gif', -file => $gif89);
}
$animate->set_image(0);
my $lab = $mw->Label(-image => $animate);
my $start = $mw->Button(
-text => 'Start',
-command => [$animate => 'start_animation', 500]);
my $stop = $mw->Button(
-text => 'Stop',
-command => [$animate => 'stop_animation']);If no images are specified, the program defaults to the multiframe "Powered by Perl" GIF89 image, as Figure 17-16 shows.
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| 17.8. The Compound Image Type |  | 17.10. tkneko—Animating the Neko on a Canvas |
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