Non-linear filters

LocalFilters provides a number of non-linear filters such as the bilateral filter and mathematical morphology filters. The latter are described in the Section Non-linear morphological filters.

The bilateral filter

Applying the bilateral filter on array A writes:

bilateralfilter([T=float(eltype(A)),] A, F, G, ...)

Argument F specifies how to smooth the differences in values. It may be function which takes two values from A as arguments and returns a nonnegative weight. It may be a real which is assumed to be the standard deviation of a Gaussian.

Arguments G, ... specify the settings of the distance filter for smoothing differences in coordinates. There are several possibilities:

• G, ... can be a single argument specifying a kernel (see Section Simple rules for specifying neighborhoods and kernels).

• Argument G may be a function taking as argument the Cartesian index of the coordinate differences and returning a nonnegative weight. Argument G may also be a real specifying the standard deviation of the Gaussian used to compute weights. Subsequent arguments ... are to specify the neighborhood where to apply the distance filter function, they can be anything that may defined a neighborhood (again see Section Simple rules for specifying neighborhoods and kernels). If a standard deviation σ is specified for G with no subsequent arguments, a default window of radius 3σ is assumed.

Optional argument T can be used to force the element type used for (most) computations. This argument is needed if the element type of A is not a real.

See bilateralfilter! for an in-place version of this function.

bilateralfilter!([T=float(eltype(A)),] dst, A, F, G, ...) -> dst

overwrites dst with the result of applying the bilateral filter on array A and returns dst.

See bilateralfilter for a description of the other arguments than dst.

See wikipedia for a description of the bilateral filter.