Extension:Painting

Painting is a MediaWiki extension that allows bitmap collaborative drawing. You can download it here.

When the painting tag is put in a wiki page, a java applet is displayed, and it downloads the last version of the image (stored in the same HTTP server as Mediawiki's). It allows users to paint on the image, and to save it, by calling a PHP servlet with HTTP + POST and thus uploading the image modified by the user.