sub _generate_captcha {
    my $self = shift;
    my ($app, $code, $format) = @_;
    $format ||= 'png';
    my $len = LENGTH();

    my $cfg = $app->config;
    my $base = $cfg->CaptchaSourceImageBase;
    unless ($base) {
        require File::Spec;
        $base = File::Spec->catfile(MT->instance->config_dir, 'mt-stat
+ic', 'images', 'captcha-source');
        $base = undef unless (-d $base);
    }
    return $app->error($app->translate('You need to configure CaptchaS
+ourceImageBase.'))
        unless $base;

    require Image::Magick;
    my $imbase = Image::Magick->new(magick=>'png')
        or return $app->error($app->translate("Image creation failed."
+));

    # Read the predefined letter PNG for each letter in $code
    my $x = $imbase->Read(map { File::Spec->catfile($base, $_ . '.png'
+) }
                          split(//, $code));
    if ($x) {
        return $app->error($app->translate("Image error: [_1]", $x));
    }

    # Futz with the size and blurriness of each letter
    foreach my $i (0..($len - 1)) {
        my $a = int rand int(WIDTH() / 14);
        my $b = int rand int(HEIGHT() / 12);

        $imbase->[$i]->Resize(width => $a, height => $b, blur => rand(
+3));
    }

    # Combine all the individual tiles into one block
    my $tile_geom    = join('x', $len, 1);
    my $geometry_str = join('x', WIDTH(), HEIGHT());
    my $im = $imbase->Montage(geometry => $geometry_str,
                              tile     => $tile_geom);
    $im->Blur();

    # Add some lines and dots to the image
    for my $i (0..($len * WIDTH() * HEIGHT() / 14+200-1)) {
        my $a = int rand($len * WIDTH());
        my $b = int rand HEIGHT();
        my $c = int rand($len * WIDTH());
        my $d = int rand HEIGHT();
        my $index = $im->Get("pixel[$a, $b]");


        if ($i < ($len * WIDTH() * HEIGHT() / 14+200) / 100) {
        $im->Draw(primitive => 'line',
                      stroke    => $index,
                      points    => "$a, $b, $c, $d");
        } elsif ($i < ($len * WIDTH() * HEIGHT() / 14+200) / 2) {
            $im->Set("pixel[$c, $d]" => $index);
        } else {
            $im->Set("pixel[$c, $d]" => "black");
        }
    }

    # Read in the background file
    my $a = int rand(5) + 1;
    my $background = Image::Magick->new();
    $background->Read(File::Spec->catfile($base, 'background' . $a . '
+.png'));
    $background->Resize(width => ($len * WIDTH()), height => HEIGHT())
+;
    $im->Composite(compose => "Bumpmap",
                   tile    => 'False',
                   image   => $background);
    $im->Modulate(brightness => 105);
    $im->Border(fill     => 'black',
                width    => 1,
                height   => 1,
                geometry => join('x', WIDTH() * $len, HEIGHT()));

    my @blobs = $im->ImageToBlob(magick=>$format);
    return $blobs[0];
}
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