164 lines
4.3 KiB
C
164 lines
4.3 KiB
C
/* creates an butterworth filter.
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*
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* 02/01/14
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* - from butterworth.c
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*/
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/*
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This file is part of VIPS.
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VIPS is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA
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*/
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/*
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These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
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*/
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/*
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#define VIPS_DEBUG
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*/
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif /*HAVE_CONFIG_H*/
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#include <glib/gi18n-lib.h>
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <math.h>
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#include <vips/vips.h>
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#include "pcreate.h"
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#include "point.h"
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#include "pmask.h"
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G_DEFINE_TYPE( VipsMaskButterworth, vips_mask_butterworth,
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VIPS_TYPE_MASK );
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static double
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vips_mask_butterworth_point( VipsMask *mask, double dx, double dy )
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{
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VipsMaskButterworth *butterworth = (VipsMaskButterworth *) mask;
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double order = butterworth->order;
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double fc = butterworth->frequency_cutoff;
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double ac = butterworth->amplitude_cutoff;
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double cnst = (1.0 / ac) - 1.0;
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double fc2 = fc * fc;
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double d = dx * dx + dy * dy;
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if( d == 0 )
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return( 0 );
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else
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return( 1.0 / (1.0 + cnst * pow( fc2 / d, order )) );
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}
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static void
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vips_mask_butterworth_class_init( VipsMaskButterworthClass *class )
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{
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GObjectClass *gobject_class = G_OBJECT_CLASS( class );
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VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS( class );
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VipsMaskClass *mask_class = VIPS_MASK_CLASS( class );
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gobject_class->set_property = vips_object_set_property;
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gobject_class->get_property = vips_object_get_property;
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vobject_class->nickname = "mask_butterworth";
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vobject_class->description = _( "make a butterworth filter" );
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mask_class->point = vips_mask_butterworth_point;
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VIPS_ARG_DOUBLE( class, "order", 6,
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_( "Order" ),
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_( "Filter order" ),
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VIPS_ARGUMENT_REQUIRED_INPUT,
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G_STRUCT_OFFSET( VipsMaskButterworth, order ),
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1.0, 1000000.0, 1.0 );
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VIPS_ARG_DOUBLE( class, "frequency_cutoff", 7,
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_( "Frequency cutoff" ),
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_( "Frequency cutoff" ),
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VIPS_ARGUMENT_REQUIRED_INPUT,
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G_STRUCT_OFFSET( VipsMaskButterworth, frequency_cutoff ),
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0.0, 1000000.0, 0.5 );
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VIPS_ARG_DOUBLE( class, "amplitude_cutoff", 8,
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_( "Amplitude cutoff" ),
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_( "Amplitude cutoff" ),
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VIPS_ARGUMENT_REQUIRED_INPUT,
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G_STRUCT_OFFSET( VipsMaskButterworth, amplitude_cutoff ),
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0.0, 1.0, 0.5 );
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}
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static void
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vips_mask_butterworth_init( VipsMaskButterworth *butterworth )
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{
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butterworth->order = 1.0;
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butterworth->frequency_cutoff = 0.5;
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butterworth->amplitude_cutoff = 0.5;
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}
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/**
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* vips_mask_butterworth:
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* @out: (out): output image
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* @width: image size
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* @height: image size
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* @order: filter order
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* @frequency_cutoff: frequency threshold
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* @amplitude_cutoff: amplitude threshold
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* @...: %NULL-terminated list of optional named arguments
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*
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* Optional arguments:
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*
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* * @nodc: don't set the DC pixel
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* * @reject: invert the filter sense
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* * @optical: coordinates in optical space
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* * @uchar: output a uchar image
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*
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* Make an butterworth high- or low-pass filter, that is, one with a variable,
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* smooth transition
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* positioned at @frequency_cutoff, where @frequency_cutoff is in
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* range 0 - 1. The shape of the curve is controlled by
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* @order --- higher values give a sharper transition. See Gonzalez and Wintz,
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* Digital Image Processing, 1987.
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*
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* See also: vips_mask_ideal().
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*
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* Returns: 0 on success, -1 on error
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*/
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int
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vips_mask_butterworth( VipsImage **out, int width, int height,
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double order, double frequency_cutoff, double amplitude_cutoff, ... )
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{
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va_list ap;
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int result;
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va_start( ap, amplitude_cutoff );
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result = vips_call_split( "mask_butterworth", ap,
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out, width, height,
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order, frequency_cutoff, amplitude_cutoff );
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va_end( ap );
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return( result );
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}
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