3.2.4 Non-parametric methods summary
Two clear advantages of the non-parametric methods are i. they are
fast in training and usage and ii. they are theoretically independent
to the shape of skin distribution (which is not true for explicit skin
cluster definition and parametric skin modelling). The disadvantages
are much storage space required and inability to interpolate
or generalize the training data. If, for example, we consider RGB
quantized to 8 bits per color, we’ll need an array of 224 elements to
store skin probabilities. To reduce the amount of needed memory
and to account for possible training data sparsity, coarser colorspace
samplings are used - 128x128x128, 64x64x64 and 32x32x32. The
evaluation of different RGB samplings in [Jones and Rehg 1999]
has shown, that 32x32x32 shows the best performance