An American academic is creating a searchable database of 12 million historical copyright-free images.

Kalev Leetaru has already uploaded 2.6 million pictures to Flickr, which are searchable thanks to tags that have been automatically added.

The photos and drawings are sourced from more than 600 million library book pages scanned in by the Internet Archive organization.

The images have been difficult to access until now.

Mr Leetaru said digitization projects had so far focused on words and ignored pictures.