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 Mathematical morphology section.

The bilateral filter

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

yields the result of applying the bilateral filter on array A.

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 LocalFilters.Kernel instance (specified as a single argument).

• 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 a Neighborhood object such as a RectangularBox or anything that may defined a neighborhood such as an odd integer assumed to be the width of the neighborhood along every dimensions of A. 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.