The Batch Custom Derivatives plugin adds a new action to the
photo batch manager labeled 'Generate custom image size' which creates
any missing registered custom derivative images. The plugin also
adds two WebService APIs to support the new batch action.

The install also includes a Perl script called piwigo_deriv.pl
that allows the creation of either regular or custom derivative
images directly from the command line (or as a background cron job).

New WebService APIs:
- bcd.getCustomDerivativeTypes
- bcd.getMissingCustomDerivatives (Admin only)