stir::ArrayFilter1DUsingConvolution< elemT > Class Template Reference

This class implements convolution of a 1D array with an arbitrary (i.e. potentially non-symmetric) kernel. More...

#include "stir/ArrayFilter1DUsingConvolution.h"

Inheritance diagram for stir::ArrayFilter1DUsingConvolution< elemT >:

Public Member Functions
	ArrayFilter1DUsingConvolution ()
	Construct a trivial filter.
	ArrayFilter1DUsingConvolution (const VectorWithOffset< elemT > &filter_kernel, const BoundaryConditions::BC bc=BoundaryConditions::zero)
	Construct the filter given the kernel coefficients. More...
bool	is_trivial () const override
	checks if the kernel corresponds to a trivial filter operation More...
Succeeded	get_influencing_indices (IndexRange< 1 > &influencing_indices, const IndexRange< 1 > &output_indices) const override
Succeeded	get_influenced_indices (IndexRange< 1 > &influenced_indices, const IndexRange< 1 > &input_indices) const override
Public Member Functions inherited from stir::ArrayFunctionObject_2ArgumentImplementation< 1, elemT >
void	operator() (Array< num_dimensions, elemT > &array) const override
	in-place modification of array, implemented inline
void	operator() (Array< num_dimensions, elemT > &out_array, const Array< num_dimensions, elemT > &in_array) const override
	result stored in another array More...
Public Member Functions inherited from stir::ArrayFunctionObject< num_dimensions, elemT >
virtual Succeeded	get_influencing_indices (IndexRange< num_dimensions > &influencing_indices, const IndexRange< num_dimensions > &output_indices) const
	sets the range of indices that influences the result in a set of coordinates output_indices More...
virtual Succeeded	get_influenced_indices (IndexRange< num_dimensions > &influenced_indices, const IndexRange< num_dimensions > &input_indices) const
	sets the range of indices that gets influenced by a set of coordinate input_indices More...

Additional Inherited Members
Protected Member Functions inherited from stir::ArrayFunctionObject_2ArgumentImplementation< 1, elemT >
virtual void	do_it (Array< num_dimensions, elemT > &out_array, const Array< num_dimensions, elemT > &in_array) const=0

Detailed Description

template<typename elemT>
class stir::ArrayFilter1DUsingConvolution< elemT >

This class implements convolution of a 1D array with an arbitrary (i.e. potentially non-symmetric) kernel.

Convolution is non-periodic:

Note that for most kernels, the above convention means that the zero- index of the kernel corresponds to the peak in the kernel.

By default, zero boundary conditions are used, i.e. elements of the input array that are outside its index range are considered to be 0.

Currently, "constant" boundary conditions are also implemented, i.e. elements of the input array that are outside its index range are considered to the same as the nearest element in the array (i.e. first element on the "left" and last element on the "right").

Example 1

A straightforward low-pass filter, with a symmetric kernel

VectorWithOffset<float> kernel(-1,1);
kernel[-1] = kernel[1] = .25F; kernel[0] = 0.5F;
ArrayFilter1DUsingConvolution<float> lowpass_filter(kernel);

Example 2

A filter which shifts the output 1 index to the right, i.e.

VectorWithOffset<float> kernel(1,1);
kernel[1] = 1.F;
ArrayFilter1DUsingConvolution<float> right_shift_filter(kernel);

Warning

1 argument operator() currently leaves the array with the the same index range, i.e. it does not extend it with the kernel size or so.

See also

ArrayFilter1DUsingSymmetricConvolution for an implementation when the kernel is symmetric. (Note: it's not clear if that implementation results in faster execution).

Todo:

implement other boundary conditions

Constructor & Destructor Documentation

ArrayFilter1DUsingConvolution()

template<typename elemT >

stir::ArrayFilter1DUsingConvolution< elemT >::ArrayFilter1DUsingConvolution	(	const VectorWithOffset< elemT > &	filter_kernel,
		const BoundaryConditions::BC	bc = BoundaryConditions::zero
	)

Construct the filter given the kernel coefficients.

Currently bc has to be BoundaryConditions::zero or BoundaryConditions::constant

Member Function Documentation

is_trivial()

template<typename elemT >

bool stir::ArrayFilter1DUsingConvolution< elemT >::is_trivial ( ) const

overridevirtual

checks if the kernel corresponds to a trivial filter operation

trivial means, either the kernel has 0 length, or length 1 and its only element is 1

Implements stir::ArrayFunctionObject< num_dimensions, elemT >.

References stir::error(), stir::VectorWithOffset< T >::get_length(), stir::VectorWithOffset< T >::get_max_index(), and stir::VectorWithOffset< T >::get_min_index().

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The documentation for this class was generated from the following files:

• /home/sirfuser/devel/STIRdistrib/STIR/src/include/stir/ArrayFilter1DUsingConvolution.h
• /home/sirfuser/devel/STIRdistrib/STIR/src/buildblock/ArrayFilter1DUsingConvolution.cxx