Figure 2:

Haar basis functions and computation of Haar filter responses. Responses are computed by subtracting the cumulative sum of the image intensities within black and white regions. (a) Varying the scale of the basis filter function to capture fine-scale anatomical features. (b) Computing the response of a single Haar basis filter by translating the filer across the image. (c) Multiple filter responses resulting from basis filter translations at ∇k intervals. (d) Different types of Haar basis functions investigated. (e) Basis filter variations by changing black/white region proportions. φ¹ and φ² basis filters are given as examples where variation filters were obtained for all 6 basis filter types in (d).