prometheus is a distributed digital image archive that currently makes more than 2,998,000 images of over 115 databases from institutes, research facilities and museums researchable on a common user interface.

Situated at the Institute of Art History of the University of Cologne, prometheus is supported by the non-profit association prometheus e.V. which promotes the ongoing developments of the digital media for science and research.

SignupSign up for prometheus

Image series of the week

Playing Cards
#promvent23 – Playing cards have their origins in East Asia. Printed sheets of paper were made in China before the birth of Christ and initially served primarily mystical purposes. | more...


For about two years now, there is an image similiarity search in prometheus that allows you to find similar images within the image inventory based on one image.
It was developed and integrated within Task Area 3 of the NFDI4Culture project by Francisco Mondaca and Jörg Koch.
On the basis of the self-supervised learning algorithm SwAV (Swapping Assignments between Views), image vectors were created that are pre-calculated for all images in the image archive and stored in the index so the search engine’s queries is reduced to calculating the distance between these vectors stored in the index. For all new images in prometheus, additional image vectors are created at regular intervals (started just recently) and stored in the index.

You will find four similar images under the single image view.

By clicking on „Show all“ you can access the view of all similar images of the winter landscape we selected.