Compute Gabors at (8) different orientations and (5) scales.
Each image point -> a point in an 80 dimensional space (each Gabor output is complex).
Compare histograms in 80D
This is hard part.
Dividing space into regular buckets doesnt work.
Cluster points
Assign each point to a cluster
Implicitly, this partitions space more
intelligently.
Compare using Chi-Squared or whatever you like.