core/vil/algo/vil_gauss_filter.h File Reference

Smooths images. More...

#include <vcl_vector.h>
#include <vil/vil_image_view.h>
#include <vil/algo/vil_convolve_1d.h>
#include <vil/vil_transpose.h>

Go to the source code of this file.

Classes
class	vil_gauss_filter_5tap_params
Functions
template<class srcT , class destT >
void	vil_gauss_filter_5tap (const srcT src_im, vcl_ptrdiff_t src_ystep, unsigned ni, unsigned nj, destT dest_im, vcl_ptrdiff_t dest_ystep, const vil_gauss_filter_5tap_params &params, destT *work)
	Smooth a single plane src_im to produce dest_im.
template<class srcT , class destT >
void	vil_gauss_filter_5tap (const vil_image_view< srcT > &src_im, vil_image_view< destT > &dest_im, const vil_gauss_filter_5tap_params &params, vil_image_view< destT > &work)
	Smooth a src_im to produce dest_im.
template<class srcT , class destT >
void	vil_gauss_filter_5tap (const vil_image_view< srcT > &src_im, vil_image_view< destT > &dest_im, const vil_gauss_filter_5tap_params &params)
	Smooth a src_im to produce dest_im.
void	vil_gauss_filter_gen_ntap (double sd, unsigned diff, vcl_vector< double > &filter_dest)
	Generate an n-tap FIR filter from a Gaussian function.
template<class srcT , class destT >
void	vil_gauss_filter_1d (const vil_image_view< srcT > &src_im, vil_image_view< destT > &dest_im, double sd, unsigned half_width)
	Smooth a src_im to produce dest_im with gaussian of width sd.
template<class srcT , class destT >
void	vil_gauss_filter_2d (const vil_image_view< srcT > &src_im, vil_image_view< destT > &dest_im, double sd, unsigned half_width, vil_convolve_boundary_option boundary=vil_convolve_zero_extend)
	Smooth a src_im to produce dest_im with gaussian of width sd.
template<class srcT , class destT >
void	vil_gauss_filter_2d (const vil_image_view< srcT > &src_im, vil_image_view< destT > &dest_im, double sd_i, unsigned half_width_i, double sd_j, unsigned half_width_j, vil_convolve_boundary_option boundary=vil_convolve_zero_extend)
	Smooth a src_im to produce dest_im with gaussian of width sd.

Detailed Description

Smooths images.

Author:: Ian Scott

Definition in file vil_gauss_filter.h.

Function Documentation

template<class srcT , class destT >

void vil_gauss_filter_1d	(	const vil_image_view< srcT > &	src_im,
		vil_image_view< destT > &	dest_im,
		double	sd,
		unsigned	half_width
	)		`[inline]`

Smooth a src_im to produce dest_im with gaussian of width sd.

Generates gaussian filter of width sd, using (2*half_width+1) values in the filter. Typically half_width>3sd. Convolves this with src_im to generate dest_im.

Definition at line 120 of file vil_gauss_filter.h.

template<class srcT , class destT >

void vil_gauss_filter_2d	(	const vil_image_view< srcT > &	src_im,
		vil_image_view< destT > &	dest_im,
		double	sd,
		unsigned	half_width,
		vil_convolve_boundary_option	boundary = `vil_convolve_zero_extend`
	)		`[inline]`

Smooth a src_im to produce dest_im with gaussian of width sd.

Generates gaussian filter of width sd, using (2*half_width+1) values in the filter. Typically half_width>3sd. Convolves this with src_im to generate work_im, then applies filter vertically to generate dest_im.

Definition at line 136 of file vil_gauss_filter.h.

template<class srcT , class destT >

void vil_gauss_filter_2d	(	const vil_image_view< srcT > &	src_im,
		vil_image_view< destT > &	dest_im,
		double	sd_i,
		unsigned	half_width_i,
		double	sd_j,
		unsigned	half_width_j,
		vil_convolve_boundary_option	boundary = `vil_convolve_zero_extend`
	)		`[inline]`

Smooth a src_im to produce dest_im with gaussian of width sd.

Generates two gaussian filters of width sd_i,sd_j, using (2*half_width_i+1) values in the filter. Typically half_width>3sd. Convolves this with src_im to generate work_im, then applies filter vertically to generate dest_im.

Definition at line 167 of file vil_gauss_filter.h.

template<class srcT , class destT >

void vil_gauss_filter_5tap	(	const srcT *	src_im,
		vcl_ptrdiff_t	src_ystep,
		unsigned	ni,
		unsigned	nj,
		destT *	dest_im,
		vcl_ptrdiff_t	dest_ystep,
		const vil_gauss_filter_5tap_params &	params,
		destT *	work
	)

Smooth a single plane src_im to produce dest_im.

Applies 5 element FIR filter in x and y. Assumes dest_im has sufficient data allocated.

template<class srcT , class destT >

void vil_gauss_filter_5tap	(	const vil_image_view< srcT > &	src_im,
		vil_image_view< destT > &	dest_im,
		const vil_gauss_filter_5tap_params &	params,
		vil_image_view< destT > &	work
	)

Smooth a src_im to produce dest_im.

Applies 5 element FIR filter in x and y.

Definition at line 144 of file vil_gauss_filter.txx.

template<class srcT , class destT >

void vil_gauss_filter_5tap	(	const vil_image_view< srcT > &	src_im,
		vil_image_view< destT > &	dest_im,
		const vil_gauss_filter_5tap_params &	params
	)		`[inline]`

Smooth a src_im to produce dest_im.

Applies 5 element FIR filter in x and y.

Definition at line 91 of file vil_gauss_filter.h.

void vil_gauss_filter_gen_ntap	(	double	sd,
		unsigned	diff,
		vcl_vector< double > &	filter
	)

Generate an n-tap FIR filter from a Gaussian function.

The filter uses the equation $k D^d \exp -\frac{x^2}{2\sigma^2}$ , where D is the differential operator, and k is a normalising constant.

Parameters:

diff	The number of differential operators to apply to the filter. If you want just a normal gaussian, set diff to 0.
sd	The width of the gaussian.

The taps will be calculated using the integral of the above equation over the pixel width. However, aliasing will reduce the meaningfulness of your filter when sd << (diff+1). In most applications you will want filter.size() ~= sd*7, which will avoid significant truncation, without wasting the outer taps on near-zero values.

Definition at line 65 of file vil_gauss_filter.cxx.