I would like to take advantage of the Galleria support for data layers added in version 1.2.5.
Some implementation thoughts:
- Use the file_entity module to augment images, etc., with a layer field, e.g. a text area field. The user creates a field for this purpose or uses an existing one.
- Create a new galleria field formatter setting that optionally identifies the "layer" field.
- Change the galleria formatter view implementation to use the layer field. The layer field's rendered value is inserted into each image as an "attributes" element such that the rendered <img> tag has the 'data-layer' attribute needed by the Galleria library.
I've successfully prototyped this approach and am happy to share it if there's interest. If there is a better way, I might try to implement that too.