“…Features are first extracted from the whole image, then a feature vector x i is assigned to each node S i ⊂ S by considering the median value of each feature in the block. The feature selection process proposed in [5] has been used to select, among a wide set of texture descriptors, the most discriminant features for the proposed problem, resulting in Gabor filters [9], Local Binary Patterns [10], Sobel filter in thex direction, mean value, standard deviation and the ratio among these two values on the grey-levels of the image, computed by a sliding windows of size H. Finally, the First Order Absolute Moment (FOAM) of the grey levels [11] is also used. FOAM is an operator that computes a vector always pointing towards the strongest gray-level discontinuity and assuming magnitude close to zero when applied to the discontinuity itself.…”