Gimp::OO 1.211 review

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Gimp::OO is a Perl module with pseudo-OO for Gimp functions. SYNOPSIS use Gimp; # Gimp::OO is now part of Gimp.

License: Perl Artistic License
File size: 266K
Developer: Marc Lehmann
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Gimp::OO is a Perl module with pseudo-OO for Gimp functions.


use Gimp; # Gimp::OO is now part of Gimp.

As you might have noticed, you can sort most gimp functions fall into three groups, depending on the name-prefix: gimp_, plug_in_, extension_ etc..

Whats more, there are functions groups like gimp_image_ or gimp_selection_, operating on a common object, Images and Selection in this case.

If you only had the plain syntax, your scripts would quickly aquire the "vertical gimp syndrome":


etc. Of course, your fingers will suffer from severe injuries as well.

A solution to this situation is to use OO-syntax. Gimp plays some (very) dirty tricks and provides a number of classes, like Gimp::Image and Gimp::Palette that allow shorter identifiers to be used (all these appear with the Gimp:: prefix as well as without, i.e. Gimp::Palette is the same class as Palette).

If you call a method, Gimp tries to find a gimp function by prepending a number of prefixes until it finds a valid function:

$image = Gimp->image_new(...); # calls gimp_image_new(...)
$image = Image->new(...); # calls gimp_image_new as well
$image = new Image(...); # the same in green
Palette->set_foreground(...) # calls gimp_palette_set_foreground(..)

Return values from functions are automatically blessed (through The Magic Autobless feature ;) to their corresponding classes, i.e.

$image = new Image(...); # $image is now blessed to Gimp::Image
$image->height; # calls gimp_image_height($image)
$image->flatten; # likewise gimp_flatten($image)
$image->histogram(...); # calls gimp_histogram($image,...), since
# gimp_image_histogram does not exist
The class argument ($image in the above examples) is prepended to the argument list.

Another shortcut: many functions want a (redundant) image argument, like

$image->shear ($layer, ...)

Since all you want is to shear the $layer, not the $image, this is confusing as well. In cases like this, Gimp allows you to write:

$layer->shear (...)

And automatically infers the additional IMAGE-type argument.

As the (currently) last goodie, if the first argument is of type INT32, its name is "run_mode" and there are no other ambiguties, you can omit it, i.e. these three calls are equivalent:

plug_in_gauss_rle (RUN_NONINTERACTIVE, $image, $layer, 8, 1, 1);
plug_in_gauss_rle ($image, $layer, 8, 1, 1);
plug_in_gauss_rle ($layer, 8, 1, 1);

You can call all sorts of sensible and not-so-sensible functions, so this feature can be abused:

patterns_list Image; # will call gimp_patterns_list
quit Plugin; # will quit the Gimp, not an Plugin.

there is no image involved here whatsoever...


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