stir::RampFilter Class Reference

The ramp filter used for (2D) FBP. More...

#include "stir/analytic/FBP2D/RampFilter.h"

Inheritance diagram for stir::RampFilter:

Public Member Functions
	RampFilter (float sampledist_v, int length_v, float alpha_v=1, float fc_v=.5)
virtual std::string	parameter_info () const
Public Member Functions inherited from stir::ArrayFilterUsingRealDFTWithPadding< 1, float >
	ArrayFilterUsingRealDFTWithPadding ()
	Default constructor (trivial kernel).
Succeeded	set_kernel (const Array< num_dimensions, float > &real_filter_kernel)
	set the real kernel coefficients
Succeeded	set_kernel_in_frequency_space (const Array< num_dimensions, std::complex< float > > &kernel_in_frequency_space)
	set the complex kernel coefficients
bool	is_trivial () const override
	checks if the kernel corresponds to a trivial filter operation
Public Member Functions inherited from stir::ArrayFunctionObject_2ArgumentImplementation< num_dimensions, float >
void	operator() (Array< num_dimensions, float > &array) const override
	in-place modification of array, implemented inline
Public Member Functions inherited from stir::ArrayFunctionObject< num_dimensions, float >
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
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
Public Member Functions inherited from stir::TimedObject
void	reset_timers ()
	reset all timers kept by this object
void	stop_timers () const
	stop all timers kept by this object
void	start_timers (bool do_reset=false) const
	start all timers kept by this object
double	get_CPU_timer_value () const
	get current value of the CPU timer (since first use or last reset)
double	get_wall_clock_timer_value () const
	get current value of the wall-clock timer (since first use or last reset)

Additional Inherited Members
Protected Member Functions inherited from stir::ArrayFilterUsingRealDFTWithPadding< 1, float >
void	do_it (Array< num_dimensions, float > &out_array, const Array< num_dimensions, float > &in_array) const override
	Performs the convolution.
Protected Attributes inherited from stir::ArrayFilterUsingRealDFTWithPadding< 1, float >
Array< num_dimensions, std::complex< float > >	kernel_in_frequency_space

Detailed Description

The ramp filter used for (2D) FBP.

The filter has 2 parameters: a cut-off frequency fc and alpha which specifies the usual Hamming window (although I'm not so sure about the terminology here). So, for the "ramp filter" alpha =1. In frequency space, something like (from RampFilter.cxx)

(alpha + (1 - alpha) * cos(_PI * f / fc))

The actual implementation works differently to overcome problems with defining the ramp in frequency space (with a well-known DC offset as consequence). We therefore compute the ramp*Hanning in "ordinary" space in continuous form, do the sampling there, and then DFT it.

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

• /home/kris/devel/STIRdistrib/STIR/src/include/stir/analytic/FBP2D/RampFilter.h
• /home/kris/devel/STIRdistrib/STIR/src/analytic/FBP2D/RampFilter.cxx