1 /* creates an butterworth filter.
2 *
3 * 02/01/14
4 * - from butterworth.c
5 */
6
7 /*
8
9 This file is part of VIPS.
10
11 VIPS is free software; you can redistribute it and/or modify
12 it under the terms of the GNU Lesser General Public License as published by
13 the Free Software Foundation; either version 2 of the License, or
14 (at your option) any later version.
15
16 This program is distributed in the hope that it will be useful,
17 but WITHOUT ANY WARRANTY; without even the implied warranty of
18 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 GNU Lesser General Public License for more details.
20
21 You should have received a copy of the GNU Lesser General Public License
22 along with this program; if not, write to the Free Software
23 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
24 02110-1301 USA
25
26 */
27
28 /*
29
30 These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
31
32 */
33
34 /*
35 #define VIPS_DEBUG
36 */
37
38 #ifdef HAVE_CONFIG_H
39 #include <config.h>
40 #endif /*HAVE_CONFIG_H*/
41 #include <vips/intl.h>
42
43 #include <stdio.h>
44 #include <string.h>
45 #include <stdlib.h>
46 #include <math.h>
47
48 #include <vips/vips.h>
49
50 #include "pcreate.h"
51 #include "point.h"
52 #include "pmask.h"
53
54 typedef struct _VipsMaskButterworthRing {
55 VipsMaskButterworth parent_instance;
56
57 double ringwidth;
58
59 } VipsMaskButterworthRing;
60
61 typedef VipsMaskButterworthClass VipsMaskButterworthRingClass;
62
63 G_DEFINE_TYPE( VipsMaskButterworthRing, vips_mask_butterworth_ring,
64 VIPS_TYPE_MASK_BUTTERWORTH );
65
66 static double
vips_mask_butterworth_ring_point(VipsMask * mask,double dx,double dy)67 vips_mask_butterworth_ring_point( VipsMask *mask,
68 double dx, double dy )
69 {
70 VipsMaskButterworth *butterworth =
71 (VipsMaskButterworth *) mask;
72 VipsMaskButterworthRing *butterworth_ring =
73 (VipsMaskButterworthRing *) mask;
74
75 double order = butterworth->order;
76 double fc = butterworth->frequency_cutoff;
77 double ac = butterworth->amplitude_cutoff;
78 double ringwidth = butterworth_ring->ringwidth;
79
80 double df = ringwidth / 2.0;
81 double cnst = (1.0 / ac) - 1.0;
82 double df2 = df * df;
83 double dist = sqrt( dx * dx + dy * dy );
84
85 return( 1.0 / (1.0 + cnst * pow(
86 (dist - fc) * (dist - fc) / df2, order )) );
87 }
88
89 static void
vips_mask_butterworth_ring_class_init(VipsMaskButterworthRingClass * class)90 vips_mask_butterworth_ring_class_init(
91 VipsMaskButterworthRingClass *class )
92 {
93 GObjectClass *gobject_class = G_OBJECT_CLASS( class );
94 VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS( class );
95 VipsMaskClass *mask_class = VIPS_MASK_CLASS( class );
96
97 gobject_class->set_property = vips_object_set_property;
98 gobject_class->get_property = vips_object_get_property;
99
100 vobject_class->nickname = "mask_butterworth_ring";
101 vobject_class->description = _( "make a butterworth ring filter" );
102
103 mask_class->point = vips_mask_butterworth_ring_point;
104
105 VIPS_ARG_DOUBLE( class, "ringwidth", 20,
106 _( "Ringwidth" ),
107 _( "Ringwidth" ),
108 VIPS_ARGUMENT_REQUIRED_INPUT,
109 G_STRUCT_OFFSET( VipsMaskButterworthRing, ringwidth ),
110 0.0, 1000000.0, 0.1 );
111
112 }
113
114 static void
vips_mask_butterworth_ring_init(VipsMaskButterworthRing * butterworth_ring)115 vips_mask_butterworth_ring_init(
116 VipsMaskButterworthRing *butterworth_ring )
117 {
118 butterworth_ring->ringwidth = 0.1;
119 }
120
121 /**
122 * vips_mask_butterworth_ring:
123 * @out: (out): output image
124 * @width: image size
125 * @height: image size
126 * @order: filter order
127 * @frequency_cutoff: frequency threshold
128 * @amplitude_cutoff: amplitude threshold
129 * @ringwidth: ringwidth
130 * @...: %NULL-terminated list of optional named arguments
131 *
132 * Optional arguments:
133 *
134 * * @nodc: don't set the DC pixel
135 * * @reject: invert the filter sense
136 * * @optical: coordinates in optical space
137 * * @uchar: output a uchar image
138 *
139 * Make a butterworth ring-pass or ring-reject filter, that is, one with a
140 * variable,
141 * smooth transition
142 * positioned at @frequency_cutoff of width @width, where @frequency_cutoff is
143 * in the range 0 - 1. The shape of the curve is controlled by
144 * @order --- higher values give a sharper transition. See Gonzalez and Wintz,
145 * Digital Image Processing, 1987.
146 *
147 * See also: vips_mask_ideal().
148 *
149 * Returns: 0 on success, -1 on error
150 */
151 int
vips_mask_butterworth_ring(VipsImage ** out,int width,int height,double order,double frequency_cutoff,double amplitude_cutoff,double ringwidth,...)152 vips_mask_butterworth_ring( VipsImage **out, int width, int height,
153 double order, double frequency_cutoff, double amplitude_cutoff,
154 double ringwidth, ... )
155 {
156 va_list ap;
157 int result;
158
159 va_start( ap, ringwidth );
160 result = vips_call_split( "mask_butterworth_ring", ap,
161 out, width, height,
162 order, frequency_cutoff, amplitude_cutoff, ringwidth );
163 va_end( ap );
164
165 return( result );
166 }
167