Nicholas Dowson at the University of Surrey



Mutual Info.





Welcome to Nicholas Dowson's homepage at the University of Surrey

I joined the Centre for Vision Speech and Signal Processing (CVSSP) under the supervision of Richard Bowden in 2003. I hope to be complete by September 2006.

My PhD work is in the field of Computer Vision, specialising in two main areas:

  • Tracking image patches through video sequences as they change in appearance.
  • Using Mutual Information is a measure of similarity between two images patches.

One of the main outputs of this work is warthog: short for (WA)rp (R)eference to (T)emplate f(h)or (O)ptimal (G)raphic. This is a matlab module which aligns a template to a reference image by min/maximising a similarity function. You can download it from the Downloads section.

The module is fast and supports many options, including:

  • 6 similarity functions (Sum of Square Differences, Normalised Correlation, standard MI, Post-Parzen MI, In-Parzen MI, and Partial Volume Estimated MI)
  • 4 warp functions (Translation, Rotation, Similarity and Affine)
  • 5 optimisation methods (including Powell and Levenberg Marquardt). Analytic derivatives are available for all the above functions.


This work would not have been possible without financial assistance in the form of a grant from the CVSSP, and an ORS Scholarship for the Department of Trade and Skills, UK.

You can email me at:

Updated: 6 July 2006.