158 lines
4.2 KiB
C
158 lines
4.2 KiB
C
/* creates an ideal filter.
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*
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* 02/01/14
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* - from ideal.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 <vips/intl.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( VipsMaskIdeal, vips_mask_ideal, VIPS_TYPE_MASK );
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static double
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vips_mask_ideal_point( VipsMask *mask, double dx, double dy )
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{
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VipsMaskIdeal *ideal = (VipsMaskIdeal *) mask;
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double fc = ideal->frequency_cutoff;
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double dist2 = dx * dx + dy * dy;
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double fc2 = fc * fc;
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return( dist2 <= fc2 ? 0.0 : 1.0 );
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}
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static void
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vips_mask_ideal_class_init( VipsMaskIdealClass *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_ideal";
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vobject_class->description = _( "make an ideal filter" );
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mask_class->point = vips_mask_ideal_point;
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VIPS_ARG_DOUBLE( class, "frequency_cutoff", 6,
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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( VipsMaskIdeal, frequency_cutoff ),
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0.0, 1000000.0, 0.5 );
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}
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static void
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vips_mask_ideal_init( VipsMaskIdeal *ideal )
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{
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ideal->frequency_cutoff = 0.5;
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}
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/**
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* vips_mask_ideal:
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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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* @frequency_cutoff: threshold at which filter ends
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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 ideal high- or low-pass filter, that is, one with a sharp cutoff
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* positioned at @frequency_cutoff, where @frequency_cutoff is in
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* the range 0 - 1.
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*
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* This operation creates a one-band float image of the specified size.
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* The image has
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* values in the range [0, 1] and is typically used for multiplying against
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* frequency domain images to filter them.
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* Masks are created with the DC component at (0, 0). The DC pixel always
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* has the value 1.0.
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*
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* Set @nodc to not set the DC pixel.
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*
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* Set @optical to position the DC component in the centre of the image. This
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* makes the mask suitable for multiplying against optical Fourier transforms.
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* See vips_wrap().
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*
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* Set @reject to invert the sense of
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* the filter. For example, low-pass becomes low-reject.
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*
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* Set @uchar to output an 8-bit unsigned char image rather than a
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* float image. In this case, pixels are in the range [0 - 255].
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*
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* See also: vips_mask_ideal(), vips_mask_ideal_ring(),
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* vips_mask_ideal_band(), vips_mask_butterworth(),
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* vips_mask_butterworth_ring(), vips_mask_butterworth_band(),
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* vips_mask_gaussian(), vips_mask_gaussian_ring(),
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* vips_mask_gaussian_band().
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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_ideal( VipsImage **out, int width, int height,
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double frequency_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, frequency_cutoff );
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result = vips_call_split( "mask_ideal", ap, out, width, height,
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frequency_cutoff );
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va_end( ap );
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return( result );
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}
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