Computation of HPS and VPS distances

This demo allows the user to compute the HPS and VPS distance of a CPS pattern. This can be used to detect what class of printers was used to generate the analyzed document. The output gives the computed HPS and VPS distances (in [inch]) and also the image with the extracted dots.
More information CPS codes (a.k.a. tracking dots, yellow dots) can be found on the website of the Electronic Frontier Foundation

For further details please refer to:

J. van Beusekom, M. Schreyer, T. M. Breuel: Automatic Counterfeit Protection System Code Classification
J. S. Tweedy. Class characteristics of counterfeit protection system codes of color laser copiers. Journal of the American Society of Questioned Document Examiners, 4(2):5366, 2001


You can either submit an image through the form interface, or you can submit it programmatically through HTTP.

Form Interface

File (max. 50MByte):

Resolution [dpi]

If you do not have an image at hand or want to try some of our images, try one of these (note that results are cached, so this is faster than using a new image):

Programmatic Interface

To submit your image programmatically, you can simply POST to this URL; the image should be a parameter named "imagefile".

From the command line, you can do this using:

curl -D header.out -F 'imagefile=@input.png;type=image/png;resolution=300' > output.png

You can also do this easily using the HTTP implementation in your favorite programming language (C#, Python, Java, Perl, etc.).