conv.c File Reference

Convolution functions. More...

#include <string.h>
#include "conv.h"

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Defines
#define	CLAMP(X, A, B)   (((X) < (A)) ? (A) : (((X) > (B)) ? (B) : (X)))
	Clamp X to [A, B].
Functions
void	SampledConv1D (float *Dest, int DestStride, const float *Src, int SrcStride, filter Filter, boundaryext Boundary, int N, int nStart, int nStep, int nEnd)
	(Sub)sampled 1D FIR convolution
void	SeparableConv2D (float *Dest, float *Buffer, const float *Src, filter FilterX, filter FilterY, boundaryext Boundary, int Width, int Height, int NumChannels)
	Separable 2D FIR convolution with constant boundary extension.
filter	MakeFilter (float *Coeff, int Delay, int Length)
	Make a filter.
filter	AllocFilter (int Delay, int Length)
	Allocate memory for a 1D FIR filter with length Length.
int	IsNullFilter (filter Filter)
	Tests whether a filter is NULL.
filter	GaussianFilter (double Sigma, int R)
	Construct an FIR approximation of a Gaussian filter.
boundaryext	GetBoundaryExt (const char *Boundary)
	Get function pointer to boundary extension function.
Variables
const filter	NullFilter = {NULL, 0, 0}
	NULL filter object.

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Detailed Description

Convolution functions.

Author:

Pascal Getreuer <getreuer@gmail.com>

Copyright (c) 2010-2011, Pascal Getreuer All rights reserved.

This program is free software: you can use, modify and/or redistribute it under the terms of the simplified BSD License. You should have received a copy of this license along this program. If not, see <http://www.opensource.org/licenses/bsd-license.html>.

Definition in file conv.c.

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Define Documentation

#define CLAMP	(		X,
			A,
			B
	)		(((X) < (A)) ? (A) : (((X) > (B)) ? (B) : (X)))

Clamp X to [A, B].

Definition at line 21 of file conv.c.

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Function Documentation

filter AllocFilter	(	int	Delay,
		int	Length
	)

Allocate memory for a 1D FIR filter with length Length.

Definition at line 161 of file conv.c.

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filter GaussianFilter	(	double	Sigma,
		int	R
	)

Construct an FIR approximation of a Gaussian filter.

Parameters:

Sigma	standard deviation of the Gaussian filter
R	support radius

This function returns an FIR filter approximating a Gaussian with standard deviation Sigma. It is the responsibility of the caller to call FreeFilter to free the filter coefficients memory when done.

The support radius of the filter is R, and the filter length is 2*R + 1. A reasonable choice for R is R = (int)ceil(4*Sigma). The coefficients are normalized to have unit sum. If Sigma is zero, then the unit impulse filter is returned.

Definition at line 193 of file conv.c.

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boundaryext GetBoundaryExt

(

const char *

Boundary

)

Get function pointer to boundary extension function.

Parameters:

Boundary

string naming the boundary extension

Returns:

function pointer on success, NULL on failure

Choices for Boundary are

• "zpd": zero-padded extension
• "sp0" or "const": constant extension
• "sp1" or "linear": linear extension
• "per": periodic extension
• "sym" or "symh": half-sample symmetric extension
• "symw": whole-sample symmetric extension
• "asym" or "asymh": half-sample antisymmetric extension
• "asymw": whole-sample antisymmetric extension

Definition at line 421 of file conv.c.

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int IsNullFilter

(

filter

Filter

)

Tests whether a filter is NULL.

Definition at line 173 of file conv.c.

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filter MakeFilter	(	float *	Coeff,
		int	Delay,
		int	Length
	)

Make a filter.

Definition at line 149 of file conv.c.

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void SampledConv1D	(	float *	Dest,
		int	DestStride,
		const float *	Src,
		int	SrcStride,
		filter	Filter,
		boundaryext	Boundary,
		int	N,
		int	nStart,
		int	nStep,
		int	nEnd
	)

(Sub)sampled 1D FIR convolution

Parameters:

Dest	pointer to memory to hold the result
DestStride	step between successive output samples
Src	pointer to the input data
SrcStride	step between successive input samples
Filter	the filter
Boundary	boundary extension
N	the length of the convolution
nStart,nStep,nEnd	sample the convolution at nStart:nStep:nEnd

Definition at line 40 of file conv.c.

void SeparableConv2D	(	float *	Dest,
		float *	Buffer,
		const float *	Src,
		filter	FilterX,
		filter	FilterY,
		boundaryext	Boundary,
		int	Width,
		int	Height,
		int	NumChannels
	)

Separable 2D FIR convolution with constant boundary extension.

Parameters:

Dest	pointer to memory to hold the result
Buffer	workspace buffer of size Width*Height
Src	pointer to the input image in row-major planar order
FilterX	the horizontal filter
FilterY	the vertical filter
Boundary	boundary extension
Width	image width
Height	image height
NumChannels	number of image channels

Definition at line 123 of file conv.c.

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Variable Documentation

const filter NullFilter = {NULL, 0, 0}

NULL filter object.

Definition at line 25 of file conv.c.