Raster Image - Fill
From RealWorld Wiki
The Fill operation is an operation plug-in, which works with raster images and fills them using the selected fill style. It can be used as a layer effect to do a gradient overlay. Alternatively, it can be used to fill selected region with pre-configured fill.
The fill can either replace or blend with the original content and it is also possible to maintain or overwrite original alpha channel.
[edit] Internals
Since it is possible to use the fill styles from a scripted filter directly, the internal configuration for this filter is skipped.