What are good filters to use for feature generation with boosting
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I'm trying to implement something like the method given here:

research.microsoft.com/en-us/um/people/viola/Pubs/MIT/tieuIJCV.pdf 

Images "similar" to a query image are retrieved from a database by using AdaBoost on features generated from the images by repeatedly filtering and downsizing them.

The paper shows images of the filters it uses for detecting basic images features (vertical lines, diagonals, corners, etc.) and states that these are separable but doesn't say exactly what the matrices are for these features. Does anyone know which matrices were used for the filters, or in general what are good choices of filters for detecting simple geometric shapes for use with boosting. 

Thanks