Filtering and Convolution (1D,2D,3D,separable)

Enumerations
enum	afConv { afConvSame = 0, afConvValid = -1, afConvFull = 1 }
	Specify which part of convolution to retain. More...
Functions
array	filter (const array &image, const array &kernel)
	Image Filter.
array	medfilt (const array &image, const unsigned height=3, const unsigned width=3)
	Median filtering within window (default 3x3)
array	convolve (const array &f1, const array &f2, const array &signal, afConv shape=afConvFull)
	Separable convolution (2D) with device arrays.
template<typename ty >
array	convolve (unsigned n1, const ty *f1, unsigned n2, const ty *f2, const array &signal, afConv shape=afConvFull)
	Separable convolution (2D) with host arrays.
array	convolve (const array &signal, const array &filter, afConv shape=afConvFull)
	Convolution (1D,2D,3D).
template<typename ty >
array	convolve (const array &signal, unsigned ndims, unsigned *dims, const ty *h_kernel, afConv shape=afConvFull)
	Convolution (1D,2D,3D) with host filter.

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Enumeration Type Documentation

enum afConv

Specify which part of convolution to retain.

   array x3 = randu(1,3), x5 = randu(1,5);
   print(convolve(x3, x5, afConvSame));  // 1x3 output
   print(convolve(x5, x3, afConvSame));  // 1x5 output
   print(convolve(x3, x5, afConvFull));  // 1x7 output
   print(convolve(x5, x3, afConvValid)); // 1x3 output
   print(convolve(x3, x5, afConvValid)); // empty output since filter bigger than signal

Enumerator:

afConvSame	the central part of the convolution that is the same size as signal (default)
afConvValid	the parts of the convolution that are computed without zero-padded edges
afConvFull	the full convolution

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Function Documentation

array af::filter	(	const array &	image,
		const array &	kernel
	)

Image Filter.

Parameters:

[in]	image
[in]	kernel	coefficient matrix

Returns:

filtered image of same size as input

Note:

Output is same size as input. Filtering done using correlation. Array values outside bounds are assumed to have zero value (0).

Examples:

examples/image/gfor_hist_demo.cpp, and examples/image/image_demo.cpp.

array af::medfilt	(	const array &	image,
		const unsigned	height = 3,
		const unsigned	width = 3
	)

Median filtering within window (default 3x3)

Parameters:

[in]	image
[in]	height	of window (default 3)
[in]	width	of window (default 3)

array af::convolve	(	const array &	f1,
		const array &	f2,
		const array &	signal,
		afConv	shape = afConvFull
	)

Separable convolution (2D) with device arrays.

Parameters:

[in]	f1	filter along the columns (first dimension)
[in]	f2	filter along the rows (second dimension)
[in]	signal
[in]	shape	type of convolution (default: afConvFull)

Examples:

examples/misc/convolve.cpp, examples/optical_flow/optical_flow.cpp, and examples/swe/swe.cpp.

array af::convolve	(	unsigned	n1,
		const ty *	f1,
		unsigned	n2,
		const ty *	f2,
		const array &	signal,
		afConv	shape = afConvFull
	)

Separable convolution (2D) with host arrays.

Parameters:

[in]	n1	number of elements in f1
[in]	f1	host pointer containing the column filter
[in]	n2	number of elements in f2
[in]	f2	host pointer containing the row filter
[in]	signal
[in]	shape	type of convolution (default: afConvFull)

array af::convolve	(	const array &	signal,
		const array &	filter,
		afConv	shape = afConvFull
	)

Convolution (1D,2D,3D).

Parameters:

[in]	signal
[in]	filter
[in]	shape	type of convolution (default: afConvFull)

array af::convolve	(	const array &	signal,
		unsigned	ndims,
		unsigned *	dims,
		const ty *	h_kernel,
		afConv	shape = afConvFull
	)

Convolution (1D,2D,3D) with host filter.

Parameters:

[in]	signal
[in]	ndims	Number of dimensions for the filter h_kernel
[in]	dims	Array containing dimension sizes of filter h_kernel
[in]	h_kernel	Host-side array containing the filter kernel coefficients
[in]	shape	type of convolution (default: afConvFull)