Linear Methods for Image Interpolation
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lprefilt.h File Reference

Prefiltering for linear interpolation. More...

#include "linterp.h"
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Functions

void PrefilterImage (float *Data, int Width, int Height, int NumChannels, const float *alpha, int NumFilterPairs, float ConstantFactor, boundaryhandling Boundary)
 Apply a cascade of first-order recursive filter pairs to an image. More...
 
void PsfConvCoeff (float *Coeff, int NumCoeffs, float(*Psf)(float, const void *), const void *PsfParams, float(*Kernel)(float), float KernelRadius, int KernelNormalize)
 Compute PSF*kernel convolution coefficients. More...
 
int PsfPreFilter (float *Data, int Width, int Height, int NumChannels, const float *Coeff, int NumCoeffs, boundaryhandling Boundary)
 Prefiltering to adjust interpolation for PSF. More...
 

Detailed Description

Prefiltering for linear interpolation.

Author
Pascal Getreuer getre.nosp@m.uer@.nosp@m.gmail.nosp@m..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 lprefilt.h.

Function Documentation

void PrefilterImage ( float *  Data,
int  Width,
int  Height,
int  NumChannels,
const float *  alpha,
int  NumFilterPairs,
float  ConstantFactor,
boundaryhandling  Boundary 
)

Apply a cascade of first-order recursive filter pairs to an image.

Parameters
Datathe image data
Width,Height,NumChannelsimage dimensions
alphaarray of alpha values
NumFilterPairsthe number of filter pairs
ConstantFactorconstant multiplicative factor to apply
Boundarythe kind of boundary handling to use

Definition at line 132 of file lprefilt.c.

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void PsfConvCoeff ( float *  Coeff,
int  NumCoeffs,
float(*)(float, const void *)  Psf,
const void *  PsfParams,
float(*)(float)  Kernel,
float  KernelRadius,
int  KernelNormalize 
)

Compute PSF*kernel convolution coefficients.

Parameters
Coeffpointer to coefficients destination array
NumCoeffsnumber of coefficients to compute
Psfthe point-spread function (PSF)
PsfParamsparameters to pass to Psf
Kernelthe interpolation kernel or basis function to use
KernelRadiussupport radius of Kernel
KernelNormalizeif nonzero, Kernel is normalized to sum to 1

The coefficients are the convolution Coeff[m] = (Psf * Kernel)(m) for m = 0, ..., NumCoeffs - 1. Integration is approximated using adaptive Gauss-Lobatto quadrature.

The result of this routine is used by PsfPreFilter.

Definition at line 214 of file lprefilt.c.

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int PsfPreFilter ( float *  Data,
int  Width,
int  Height,
int  NumChannels,
const float *  Coeff,
int  NumCoeffs,
boundaryhandling  Boundary 
)

Prefiltering to adjust interpolation for PSF.

Parameters
Datapointer to image data to be filtered
Width,Height,NumChannelsimage dimensions
Coeffthe PSF adjustment coefficients from PsfConvCoeff
NumCoeffsnumber of coefficients
Boundaryboundary handling

Convolves Data with the inverse of Coeff[0] + Coeff[1] (z + z^-1) + Coeff[2] (z^2 + z^-2) + ... via the DCT transform. Boundary handling can be either half- or whole- sample symmetric (constant extension is not supported).

Half-sample symmetric boundary handling is considerably more efficient, about 25% shorter runtime than when using whole-sample symmetry.

Definition at line 380 of file lprefilt.c.

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