Image source is a plugin providing (possibly hierarchical) image collection to other plugins. The images should have a public URL and a few other attributes.

For example, the Blasq module provides images from the cloud services, while the LHTR editor module can embed them into the document being edited. Firstly the user selects the service to embed images from:

Then one chooses the images to add (on Blasq side):

Then one can configure parameters like previews size, alt text, alignment and so on (now on the LHTR side):

And finally (on the Blogique side, in which LHTR embeds):