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libvips/libsrc/freq_filt/fmask4th.c
John Cupitt 5494f610e2 split to trunk/branches
2007-08-29 16:23:50 +00:00

801 lines
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/* @(#) Typical filter functions
* @(#) va_list is flag, filter parameters
* @(#) The following masks are implemented in this file
* @(#) lowpass highpass filters
* @(#) flag filter shape parameters
* @(#) 0 -\> idealhpf, parameters: frequency cutoff
* @(#) 1 -\> ideallpf, parameters: frequency cutoff
* @(#) 2 -\> buthpf, parameters: order, frequency cutoff, amplitude cutoff
* @(#) 3 -\> butlpf, parameters: order, frequency cutoff, amplitude cutoff
* @(#) 4 -\> gaussianlpf, parameters: frequency cutoff, amplitude cutoff
* @(#) 5 -\> gaussianhpf, parameters: frequency cutoff, amplitude cutoff
* @(#) ring pass ring reject filters
* @(#) 6 -\> idealrpf, parameters: frequency cutoff, width
* @(#) 7 -\> idealrrf, parameters: frequency cutoff, width
* @(#) 8 -\> butrpf, parameters: order, freq cutoff, width, ampl cutoff
* @(#) 9 -\> butrrf, parameters: order, freq cutoff, width, ampl cutoff
* @(#) 10 -\> gaussianrpf, parameters: frequency cutoff, width, ampl cutoff
* @(#) 11 -\> gaussianrrf, parameters: frequency cutoff, width, ampl cutoff
* @(#) fractal filters (for filtering gaussian noises only)
* @(#) 18 -> fractal, parameters: fractal dimension
* @(#)
* @(#) Initially one forth of the coefficients is created and it is copied over
* @(#) the four quadrants for faster processing
* @(#)
* @(#) Functions in this file; for explanations see each function
* @(#)
* @(#) float *
* @(#) im__create_quarter( out, xs, ys, flag, ap )
* @(#) IMAGE *out;
* @(#) int xs, ys;
* @(#) enum mask_type flag;
* @(#) va_list ap;
* @(#)
*
* Written on: Nov 1991
* Updated on: Dec 1991
* 20/9/95 JC
* - modernised
*/
/*
This file is part of VIPS.
VIPS is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <vips/intl.h>
#include <stdio.h>
#include <math.h>
#include <stdarg.h>
#include <vips/vips.h>
#include <vips/fmask.h>
#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif /*WITH_DMALLOC*/
/************************************************************************/
/* malloc space and create normalised coefficients accross */
/* the x (horizontal) and y (vertical) direction. */
/************************************************************************/
static int
alloc( IMAGE *out, int xs, int ys, double **xd, double **yd, float **coeff )
{
int i;
double *x, *y;
float *c;
x = IM_ARRAY( out, xs/2 + 1, double );
y = IM_ARRAY( out, ys/2 + 1, double );
c = IM_ARRAY( out, (xs/2 + 1)*(ys/2 + 1), float );
if( !x || !y || !c )
return( -1 );
for( i = 0; i < ys/2 + 1; i++ )
y[i] = (i * i) / ((double) (ys*ys/4));
for( i = 0; i < xs/2 + 1; i++ )
x[i] = (i * i) / ((double) (xs*xs/4));
*xd = x; *yd = y; *coeff = c;
return( 0 );
}
/* xs and ys are the sizes of the final mask; all functions returns
* the coefficients for one forth of the final mask
*/
/************************************************************************/
/* FLAG = 0 */
/* Creates an ideal high pass filter mask */
/************************************************************************/
static float *
ideal_hpf( IMAGE *out, int xs, int ys, double fc )
{
int x, y;
float *coeff, *cpcoeff;
double *xd, *yd, fc2, distance2;
if( xs != ys || fc < 0.0 ) {
im_errormsg( "ideal_hpf: bad args" );
return( NULL );
}
if( fc > 1.0 && fc <= xs/2 )
fc2 = fc * fc * 4.0 / (double)(xs * ys);
else if( fc <= 1.0 && fc > 0.0 )
fc2 = fc * fc;
else {
im_errormsg( "ideal_hpf: bad args" );
return( NULL );
}
if( alloc( out, xs, ys, &xd, &yd, &coeff ) )
return( NULL );
cpcoeff = coeff;
for( y = 0; y < ys/2 + 1; y++ )
for( x = 0; x < xs/2 + 1; x++ ) {
distance2 = xd[x] + yd[y];
if( distance2 > fc2 )
*cpcoeff++ = 1.0;
else
*cpcoeff++ = 0.0;
}
*coeff = 1.0;
return( coeff );
}
/************************************************************************/
/* FLAG = 1 */
/* Creates an ideal low pass filter mask */
/************************************************************************/
static float *
ideal_lpf( IMAGE *out, int xs, int ys, double fc )
{
int x, y;
float *coeff, *cpcoeff;
double *xd, *yd, fc2, distance2;
if( xs != ys || fc <= 0.0 ) {
im_errormsg( "ideal_lpf: bad args" );
return( NULL );
}
if( fc > 1.0 && fc <= xs/2 )
fc2 = fc * fc * 4.0 / (double)(xs * ys);
else if( fc <= 1.0 && fc > 0.0 )
fc2 = fc * fc;
else {
im_errormsg( "ideal_lpf: bad args" );
return( NULL );
}
if( alloc( out, xs, ys, &xd, &yd, &coeff ) )
return( NULL );
cpcoeff = coeff;
for( y = 0; y < ys/2 + 1; y++ )
for( x = 0; x < xs/2 + 1; x++ ) {
distance2 = xd[x] + yd[y];
if( distance2 <= fc2 )
*cpcoeff++ = 1.0;
else
*cpcoeff++ = 0.0;
}
return( coeff );
}
/************************************************************************/
/* FLAG = 2 */
/* Creates an Butterworth high pass filter mask */
/************************************************************************/
static float *
butterworth_hpf( IMAGE *out, int xs, int ys,
double order, double fc, double ac )
{
int x, y;
float *coeff, *cpcoeff;
double *xd, *yd, fc2, distance2, cnst;
if( xs != ys || fc < 0.0 || order < 1.0 || ac <= 0.0 || ac >= 1.0 ) {
im_errormsg( "butterworth_hpf: bad args" );
return( NULL );
}
if( fc > 1.0 && fc <= xs/2 )
fc2 = fc * fc * 4.0 / (double)(xs * ys);
else if( fc <= 1.0 && fc > 0.0 )
fc2 = fc * fc;
else {
im_errormsg( "butterworth_hpf: bad args" );
return( NULL );
}
if( alloc( out, xs, ys, &xd, &yd, &coeff) )
return( NULL );
cpcoeff = coeff;
cnst = (1.0 / ac) - 1.0;
for( y = 0; y < ys/2 + 1; y++ )
for( x = 0; x < xs/2 + 1; x++ ) {
/* Leave the dc component unaltered
*/
if( x == 0 && y == 0 )
*cpcoeff++ = 1.0;
else {
distance2 = fc2 / (xd[x] + yd[y]);
*cpcoeff++ = 1.0 /
(1.0 + cnst * pow( distance2, order ));
}
}
return( coeff );
}
/************************************************************************/
/* FLAG = 3 */
/* Creates an Butterworth low pass filter mask */
/************************************************************************/
static float *
butterworth_lpf( IMAGE *out, int xs, int ys,
double order, double fc, double ac )
{
int x, y;
float *coeff, *cpcoeff;
double *xd, *yd, fc2, distance2, cnst;
if( xs != ys || fc <= 0.0 || order < 1.0 || ac >= 1.0 || ac <= 0.0 ) {
im_errormsg( "butterworth_lpf: bad args" );
return( NULL );
}
if( fc > 1.0 && fc <= xs/2 )
fc2 = fc * fc * 4.0 / (double)(xs * ys);
else if( fc <= 1.0 && fc > 0.0 )
fc2 = fc * fc;
else {
im_errormsg( "butterworth_lpf: bad args" );
return( NULL );
}
if( alloc( out, xs, ys, &xd, &yd, &coeff ) )
return( NULL );
cpcoeff = coeff;
cnst = (1.0/ac) - 1.0;
for( y = 0; y < ys/2 + 1; y++ )
for( x = 0; x < xs/2 + 1; x++ ) {
distance2 = (xd[x] + yd[y])/fc2;
*cpcoeff++ = 1.0 /
(1.0 + cnst * pow( distance2, order ));
}
return( coeff );
}
/************************************************************************/
/* FLAG = 4 */
/* Creates a gaussian high pass filter mask */
/************************************************************************/
static float *
gaussian_hpf( IMAGE *out, int xs, int ys, double fc, double ac )
{
int x, y;
float *coeff, *cpcoeff;
double *xd, *yd, fc2, distance2, cnst;
if( xs != ys || fc <= 0.0 || ac >= 1.0 || ac <= 0.0 ) {
im_errormsg( "gaussian_hpf: bad args" );
return( NULL );
}
if( fc > 1.0 && fc <= xs/2 )
fc2 = fc * fc * 4.0 / (double)(xs * ys);
else if( fc <= 1.0 && fc > 0.0 )
fc2 = fc * fc;
else {
im_errormsg( "gaussian_hpf: bad args" );
return( NULL );
}
if( alloc( out, xs, ys, &xd, &yd, &coeff ) )
return( NULL );
cpcoeff = coeff;
cnst = -log( ac );
for( y = 0; y < ys/2 + 1; y++ )
for( x = 0; x < xs/2 + 1; x++ ) {
distance2 = (xd[x] + yd[y])/fc2;
*cpcoeff++ = 1.0 - exp( -cnst * distance2 );
}
*coeff = 1.0;
return( coeff );
}
/************************************************************************/
/* FLAG = 5 */
/* Creates a gaussian low pass filter mask */
/************************************************************************/
static float *
gaussian_lpf( IMAGE *out, int xs, int ys, double fc, double ac )
{
int x, y;
float *coeff, *cpcoeff;
double *xd, *yd, fc2, distance2, cnst;
if( xs != ys || fc < 0.0 || ac >= 1.0 || ac <= 0.0 ) {
im_errormsg( "gaussian_lpf: bad args" );
return( NULL );
}
if( fc > 1.0 && fc <= xs/2 )
fc2 = fc * fc * 4.0 / (double)(xs * ys);
else if( fc <= 1.0 && fc > 0.0 )
fc2 = fc * fc;
else {
im_errormsg( "gaussian_lpf: bad args" );
return( NULL );
}
if( alloc( out, xs, ys, &xd, &yd, &coeff ) )
return( NULL );
cpcoeff = coeff;
cnst = -log( ac );
for( y = 0; y < ys/2 + 1; y++ )
for( x = 0; x < xs/2 + 1; x++ ) {
distance2 = (xd[x] + yd[y])/fc2;
*cpcoeff++ = exp( - cnst * distance2 );
}
return( coeff );
}
/************************************************************************/
/* FLAG = 6 */
/* Creates an ideal ring pass filter mask */
/* The band is a RING of internal radius fc-df and external radius fc+df*/
/************************************************************************/
static float *
ideal_rpf( IMAGE *out, int xs, int ys, double fc, double width )
{
int x, y;
float *coeff, *cpcoeff;
double *xd, *yd, df, distance2, radius1_2, radius2_2;
if( xs != ys || fc <= 0 || width <= 0 ) {
im_errormsg( "ideal_rpf: bad args" );
return( NULL );
}
df = width/2.0;
if( fc <= 1.0 && df < 1.0 && fc - df > 0.0 ) {
radius1_2 = (fc-df)*(fc-df);
radius2_2 = (fc+df)*(fc+df);
}
else if( fc - df > 1.0 && df >= 1.0 && fc <= xs/2 ) {
radius1_2 = (fc - df) * (fc - df) * 4.0 / ((double)(xs * xs));
radius2_2 = (fc + df) * (fc + df) * 4.0 / ((double)(xs * xs));
}
else {
im_errormsg( "ideal_rpf: bad args" );
return( NULL );
}
if( alloc( out, xs, ys, &xd, &yd, &coeff ) )
return( NULL );
cpcoeff = coeff;
for( y = 0; y < ys/2 + 1; y++ )
for( x = 0; x < xs/2 + 1; x++ ) {
distance2 = xd[x] + yd[y];
if( distance2 < radius2_2 && distance2 > radius1_2 )
*cpcoeff++ = 1.0;
else
*cpcoeff++ = 0.0;
}
*coeff = 1.0;
return( coeff );
}
/************************************************************************/
/* FLAG = 7 */
/* Creates an ideal band reject filter mask */
/* The band is a RING of internal radius fc-df and external radius fc+df*/
/************************************************************************/
static float *
ideal_rrf( IMAGE *out, int xs, int ys, double fc, double width )
{
int x, y;
float *coeff, *cpcoeff;
double *xd, *yd, df, distance2, radius1_2, radius2_2;
if( xs != ys || fc < 0.0 || width <= 0.0 ) {
im_errormsg( "ideal_rrf: bad args" );
return( NULL );
}
df = width/2.0;
if( fc <= 1.0 && df < 1.0 && fc - df > 0.0 ) {
radius1_2 = (fc-df)*(fc-df);
radius2_2 = (fc+df)*(fc+df);
}
else if( fc - df > 1.0 && df >= 1.0 && fc <= xs/2 ) {
radius1_2 = (fc - df) * (fc - df) * 4.0 / ((double)(xs * xs));
radius2_2 = (fc + df) * (fc + df) * 4.0 / ((double)(xs * xs));
}
else {
im_errormsg( "ideal_rrf: bad args" );
return( NULL );
}
if( alloc( out, xs, ys, &xd, &yd, &coeff ) )
return( NULL );
cpcoeff = coeff;
for( y = 0; y < ys/2 + 1; y++ )
for( x = 0; x < xs/2 + 1; x++ ) {
distance2 = xd[x] + yd[y];
if( distance2 < radius2_2 && distance2 > radius1_2 )
*cpcoeff++ = 0.0;
else
*cpcoeff++ = 1.0;
}
return( coeff );
}
/************************************************************************/
/* FLAG = 8 */
/* Creates a butterworth band pass filter mask */
/* The band is a RING of internal radius fc-df and external radius fc+df*/
/************************************************************************/
static float *
butterworth_rpf( IMAGE *out, int xs, int ys,
double order, double fc, double width, double ac )
{
int x, y;
float *coeff, *cpcoeff;
double *xd, *yd, d, df, ndf, ndf2, nfc, cnst;
if( xs != ys || fc <= 0.0 || width <= 0.0 ||
order < 1.0 || ac >= 1.0 || ac <= 0.0 ) {
im_errormsg( "butterworth_rpf: bad args" );
return( NULL );
}
df = width/2.0;
if( fc <= 1.0 && df < 1.0 && fc-df > 0.0 ) {
nfc = fc;
ndf = width/2.0;
}
else if( fc - df > 1.0 && df >= 1.0 && fc <= xs/2 ) {
nfc = fc * 2.0 /(double)xs;
ndf = width /(double)ys;
}
else {
im_errormsg( "butterworth_rpf: bad args" );
return( NULL );
}
if( alloc( out, xs, ys, &xd, &yd, &coeff ) )
return( NULL );
cpcoeff = coeff;
cnst = (1.0/ac) - 1.0;
ndf2 = ndf * ndf;
for( y = 0; y < ys/2 + 1; y++ )
for( x = 0; x < xs/2 + 1; x++ ) {
d = sqrt( xd[x] + yd[y] );
*cpcoeff++ = 1.0 /
(1.0 + cnst *
pow( (d-nfc)*(d-nfc)/ndf2, order ));
}
*coeff = 1.0;
return( coeff );
}
/************************************************************************/
/* FLAG = 9 */
/* Creates a butterworth ring reject filter mask */
/* The band is a RING of internal radius fc-df and external radius fc+df*/
/************************************************************************/
static float *
butterworth_rrf( IMAGE *out, int xs, int ys,
double order, double fc, double width, double ac )
{
int x, y;
float *coeff, *cpcoeff;
double *xd, *yd, d, df, ndf, ndf2, nfc, cnst;
if( xs != ys || fc <= 0.0 || width <= 0.0 ||
order < 1.0 || ac >= 1.0 || ac <= 0.0 ) {
im_errormsg( "butterworth_rrf: bad args" );
return( NULL );
}
df = width/2.0;
if( fc <= 1.0 && df < 1.0 && fc-df > 0.0 ) {
nfc = fc;
ndf = width/2.0;
}
else if( fc - df > 1.0 && df >= 1.0 && fc <= xs/2 ) {
nfc = fc * 2.0 /(double)xs;
ndf = width /(double)ys;
}
else {
im_errormsg( "butterworth_rrf: bad args" );
return( NULL );
}
if( alloc( out, xs, ys, &xd, &yd, &coeff ) )
return( NULL );
cpcoeff = coeff;
cnst = (1.0/ac) - 1.0;
ndf2 = ndf * ndf;
for( y = 0; y < ys/2 + 1; y++ )
for( x = 0; x < xs/2 + 1; x++ ) {
d = sqrt( xd[x] + yd[y] );
if( d == 0.0 )
*cpcoeff++ = 1.0;
else
*cpcoeff++ = 1.0 /
(1.0 + cnst * pow(
ndf2/((d-nfc)*(d-nfc)), order ));
}
return( coeff );
}
/************************************************************************/
/* FLAG = 10 */
/* Creates a gaussian band pass filter mask */
/* The band is a RING of internal radius fc-df and external radius fc+df*/
/************************************************************************/
static float *
gaussian_rpf( IMAGE *out, int xs, int ys, double fc, double width, double ac )
{
int x, y;
float *coeff, *cpcoeff;
double *xd, *yd, d, df, ndf, ndf2, nfc, cnst;
if( xs != ys || fc < 0.0 || width <= 0.0 || ac <= 0.0 || ac > 1.0 ) {
im_errormsg( "gaussian_rpf: bad args" );
return( NULL );
}
df = width/2.0;
if( fc <= 1.0 && df < 1.0 && fc - df > 0.0 ) {
nfc = fc;
ndf = width/2.0;
}
else if( fc - df > 1.0 && df >= 1.0 && fc <= xs/2 ) {
nfc = fc * 2.0 /(double) xs;
ndf = width /(double)ys;
}
else {
im_errormsg( "gaussian_rpf: bad args" );
return( NULL );
}
if( alloc( out, xs, ys, &xd, &yd, &coeff ) )
return( NULL );
cpcoeff = coeff;
cnst = -log( ac );
ndf2 = ndf * ndf;
for( y = 0; y < ys/2 + 1; y++ )
for( x = 0; x < xs/2 + 1; x++ ) {
d = sqrt( xd[x] + yd[y] );
*cpcoeff++ = exp( -cnst * (d-nfc) * (d-nfc)/ndf2 );
}
*coeff = 1.0;
return( coeff );
}
/************************************************************************/
/* FLAG = 11 */
/* Creates a gaussian band reject filter mask */
/* The band is a RING of internal radius fc-df and external radius fc+df*/
/************************************************************************/
static float *
gaussian_rrf( IMAGE *out, int xs, int ys, double fc, double width, double ac )
{
int x, y;
float *coeff, *cpcoeff;
double *xd, *yd, d, df, ndf, ndf2, nfc, cnst;
if( xs != ys || fc < 0.0 || width <= 0.0 || ac <= 0.0 || ac > 1.0 ) {
im_errormsg( "gaussian_rrf: bad args" );
return( NULL );
}
df = width/2.0;
if( fc <= 1.0 && df < 1.0 && fc - df > 0.0 ) {
nfc = fc;
ndf = width/2.0;
}
else if( fc - df > 1.0 && df >= 1.0 && fc <= xs/2 ) {
nfc = fc * 2.0 /(double) xs;
ndf = width / (double)ys;
}
else {
im_errormsg( "gaussian_rrf: bad args" );
return( NULL );
}
if( alloc( out, xs, ys, &xd, &yd, &coeff ) )
return( NULL );
cpcoeff = coeff;
cnst = -log( ac );
ndf2 = ndf * ndf;
for( y = 0; y < ys/2 + 1; y++ )
for( x = 0; x < xs/2 + 1; x++ ) {
d = sqrt( xd[x] + yd[y] );
*cpcoeff++ = 1.0 -
exp( -cnst * (d-nfc) * (d-nfc) / ndf2 );
}
return( coeff );
}
/************************************************************************/
/* FLAG = 18 */
/* Theoretically the power spectrum of a fractal surface should decay
* according to its fractal dimension
* This program should be used to create fractal images by filtering the
* power spectrum of Gaussian white noise
* More specifically according to PIET:
* since the coefficients of fractal noise
* < |vsubk|^2 > decay as 1/( |f|^(beta+1) )
* or since beta=2*H + 1, beta= 7-2*D
* < |vsubk|^2 > decay as 1/( |f|^(8-2*D) )
* and the fractal filter which should produce vsubk
* should have transfer function decaying as 1/( |f|^((beta+1)/2) )
* where f = sqrt(fsubx * fsubx + fsuby *fsuby)
* Finally the filter has transfer function decaying as
* sqrt(fsubx*fsubx+fsuby*fsuby)^(D-4) or
* (fsubx*fsubx+fsuby*fsuby)^((D-4)/2) <--- This relation is used.
* On the other hand if D=3-H, the filtermask should decay as
* (fsubx*fsubx+fsuby*fsuby)^(-(H+1)/2) , 0<H<1
* which is exactly the same as above (PIET page 108)
* Please note that when a filter mask is created to dc coefficient is
* set to 1.0 and therefore when a mask is scaled for display
* the dc coefficient appears to be wrong (it is not!!)
*/
/************************************************************************/
static float *
fractal_flt( IMAGE *out, int xs, int ys, double frdim )
{
int x, y;
float *coeff, *cpcoeff;
double *xd, *yd, distance2, cnst;
if( xs != ys || frdim <= 2.0 || frdim >= 3.0 ) {
im_errormsg( "fractal_flt: bad args" );
return( NULL );
}
if( alloc( out, xs, ys, &xd, &yd, &coeff ) )
return( NULL );
cpcoeff = coeff;
cnst = (frdim - 4.0)/2.0;
for( y = 0; y < ys/2 + 1; y++ )
for( x = 0; x < xs/2 + 1; x++ ) {
distance2 = xd[x] + yd[y];
if( distance2 == 0.0 )
*cpcoeff++ = 1.0;
else
*cpcoeff++ = pow( distance2, cnst );
}
return( coeff );
}
/* Creates one forth of the mask coefficients. If the final mask is
* xsize by xsize, one forth should have sizes (xsize/2 + 1) by (ysize/2 + 1)
* This happens because the horizontal spatial frequencies extend
* from -xsize/2 up to (xsize/2 - 1) inclusive and
* the vertical spatial frequencies
* from -ysize/2 up to (ysize/2 - 1) inclusive
* In order to calculate the spatial frequencies at location (x, y)
* the maximum spatial frequency at the horizontal direction xsize/2 and
* the maximum spatial frequency at the vertical direction ysize/2 have
* been normalised to 1.0.
* All arithmetic internally has been carried out in double precision;
* however all masks are written as floats with maximum value normalised to 1.0
*/
float *
im__create_quarter( IMAGE *out, int xs, int ys, MaskType flag, va_list ap )
{
/* May be fewer than 4 args ... but extract them all anyway. Should be
* safe.
*/
double p0 = va_arg( ap, double );
double p1 = va_arg( ap, double );
double p2 = va_arg( ap, double );
double p3 = va_arg( ap, double );
switch( flag ) {
/* High pass - low pass
*/
case MASK_IDEAL_HIGHPASS:
return( ideal_hpf( out, xs, ys, p0 ) );
case MASK_IDEAL_LOWPASS:
return( ideal_lpf( out, xs, ys, p0 ) );
case MASK_BUTTERWORTH_HIGHPASS:
return( butterworth_hpf( out, xs, ys, p0, p1, p2 ) );
case MASK_BUTTERWORTH_LOWPASS:
return( butterworth_lpf( out, xs, ys, p0, p1, p2 ) );
case MASK_GAUSS_HIGHPASS:
return( gaussian_hpf( out, xs, ys, p0, p1 ) );
case MASK_GAUSS_LOWPASS:
return( gaussian_lpf( out, xs, ys, p0, p1 ) );
/* Ring pass - ring reject.
*/
case MASK_IDEAL_RINGPASS:
return( ideal_rpf( out, xs, ys, p0, p1 ) );
case MASK_IDEAL_RINGREJECT:
return( ideal_rrf( out, xs, ys, p0, p1 ) );
case MASK_BUTTERWORTH_RINGPASS:
return( butterworth_rpf( out,
xs, ys, p0, p1, p2, p3 ) );
case MASK_BUTTERWORTH_RINGREJECT:
return( butterworth_rrf( out,
xs, ys, p0, p1, p2, p3 ) );
case MASK_GAUSS_RINGPASS:
return( gaussian_rpf( out, xs, ys, p0, p1, p2 ) );
case MASK_GAUSS_RINGREJECT:
return( gaussian_rrf( out, xs, ys, p0, p1, p2 ) );
case MASK_FRACTAL_FLT:
return( fractal_flt( out, xs, ys, p0 ) );
default:
im_errormsg( "create_quarter: unimplemented mask" );
return( NULL );
}
/*NOTREACHED*/
}
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