Automatically watermark imagery

It would be very useful if there was a feature to automatically watermark imagery either:

a) When performing a bulk upload;
b) When manually uploading images one at a time;
c) Or retrospectively applying watermarks by triggering functionality using bulk actions on the product list admin panel

This would allow customisation of the watermark to be applied - this could be simple text with ability to modify font/size/colour, or perhaps a transparent gif/png which could be uploaded.

Original images would need to be stored in case of subsequent updates to watermark, which would then need to be reapplied to existing images, or simply the need to revert to the original image without any watermark at all.