Hello monks,

I have once seen a simple but interesting animation effect somewhere, but can't find that image anymore. So I decided to reproduce the effect myself, and wrote a script that given a static input image, produces an animated gif. I succeeded, and now I have that script, I'd like to share. However, Perlmonks doesn't allow embedding images, so I'll include here the source only, while the step-by-step tutorial with intermediate images and deeper explanations shall be accessible here:

Hypnotic effect

Here's the source: 


use strict;
use Prima 1.27;
use IPA qw(Misc);
die "need image\n" unless @ARGV;

my $source = Prima::Image-> load($ARGV[0]);
die "Can't load $ARGV[0]:$@\n" unless $source;
$source-> type(im::bpp24);
    
my $mask = Prima::Image-> new(
    width  => $source-> width  * 2,
    height => $source-> height * 2,
    type   => im::BW,
);
my @size = $mask-> size;
my $max = $size[$size[0] < $size[1]] / 2;

my $step = 2;
my @centers  = (
    [ 243, 159 ],
    [ 208, 150 ],
    [ 233, 111 ],
);

my @img;
for ( my $offset = 0; $offset < $step * 2; $offset++) {
    $mask-> begin_paint;
    $mask-> clear;
    $mask-> lineWidth( $step);
    my @center = map { int($_ + .5) } ($size[0] / 2, $size[1] / 2);
    for ( my $i = 0; $i < $max; $i += $step * 2) {
        my $d = $offset * 2 + $i * 2;
        $mask-> ellipse( @center, $d, $d);
    }
    $mask-> end_paint;
    
    my @channels = @{ IPA::Misc::split_channels( $source, 'rgb') };
    for ( my $i = 0; $i < @channels; $i++) {
        $channels[$i]-> put_image(
            $centers[$i]->[0] - $center[0],
            $centers[$i]->[1] - $center[1],
            $mask, rop::AndPut
        );
    }
    my $output = combine_channels( \@channels, 'rgb');
    $output-> type(im::bpp8);
    push @img, $output; 

}

my $saved = Prima::Image-> save(
    "output.gif",
    images    => \@img,
    loopCount => 0,
    delayTime => 5,
);
die "Cannot save output.gif:$@\n" unless $saved == @img;

[download]

Comments and suggestions are welcome.

In reply to Image manipulation with Prima by dk

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