Mathematica not only includes highly optimized implementations of standard image processing filters, but also uses its general symbolic architecture to allow arbitrarily sophisticated filtering and neighborhood processing strategies to be set up using the full mathematical and algorithmic power of Mathematica.
GaussianFilter — Gaussian and Gaussian derivatives filter
DerivativeFilter — general-order derivative filter
Masking — specify the image or graphics description of the region to which filters will be applied
ImageFilter — apply an arbitrary function to blocks of pixel values
ImageData — extract an array of data from an image
Partition — generalized partitioning
CellularAutomaton — general cellular automaton