1 /* creates an ideal filter.
2 *
3 * 02/01/14
4 * - from ideal.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 G_DEFINE_TYPE( VipsMaskIdeal, vips_mask_ideal, VIPS_TYPE_MASK );
55
56 static double
vips_mask_ideal_point(VipsMask * mask,double dx,double dy)57 vips_mask_ideal_point( VipsMask *mask, double dx, double dy )
58 {
59 VipsMaskIdeal *ideal = (VipsMaskIdeal *) mask;
60 double fc = ideal->frequency_cutoff;
61
62 double dist2 = dx * dx + dy * dy;
63 double fc2 = fc * fc;
64
65 return( dist2 <= fc2 ? 0.0 : 1.0 );
66 }
67
68 static void
vips_mask_ideal_class_init(VipsMaskIdealClass * class)69 vips_mask_ideal_class_init( VipsMaskIdealClass *class )
70 {
71 GObjectClass *gobject_class = G_OBJECT_CLASS( class );
72 VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS( class );
73 VipsMaskClass *mask_class = VIPS_MASK_CLASS( class );
74
75 gobject_class->set_property = vips_object_set_property;
76 gobject_class->get_property = vips_object_get_property;
77
78 vobject_class->nickname = "mask_ideal";
79 vobject_class->description = _( "make an ideal filter" );
80
81 mask_class->point = vips_mask_ideal_point;
82
83 VIPS_ARG_DOUBLE( class, "frequency_cutoff", 6,
84 _( "Frequency cutoff" ),
85 _( "Frequency cutoff" ),
86 VIPS_ARGUMENT_REQUIRED_INPUT,
87 G_STRUCT_OFFSET( VipsMaskIdeal, frequency_cutoff ),
88 0.0, 1000000.0, 0.5 );
89
90 }
91
92 static void
vips_mask_ideal_init(VipsMaskIdeal * ideal)93 vips_mask_ideal_init( VipsMaskIdeal *ideal )
94 {
95 ideal->frequency_cutoff = 0.5;
96 }
97
98 /**
99 * vips_mask_ideal:
100 * @out: (out): output image
101 * @width: image size
102 * @height: image size
103 * @frequency_cutoff: threshold at which filter ends
104 * @...: %NULL-terminated list of optional named arguments
105 *
106 * Optional arguments:
107 *
108 * * @nodc: don't set the DC pixel
109 * * @reject: invert the filter sense
110 * * @optical: coordinates in optical space
111 * * @uchar: output a uchar image
112 *
113 * Make an ideal high- or low-pass filter, that is, one with a sharp cutoff
114 * positioned at @frequency_cutoff, where @frequency_cutoff is in
115 * the range 0 - 1.
116 *
117 * This operation creates a one-band float image of the specified size.
118 * The image has
119 * values in the range [0, 1] and is typically used for multiplying against
120 * frequency domain images to filter them.
121 * Masks are created with the DC component at (0, 0). The DC pixel always
122 * has the value 1.0.
123 *
124 * Set @nodc to not set the DC pixel.
125 *
126 * Set @optical to position the DC component in the centre of the image. This
127 * makes the mask suitable for multiplying against optical Fourier transforms.
128 * See vips_wrap().
129 *
130 * Set @reject to invert the sense of
131 * the filter. For example, low-pass becomes low-reject.
132 *
133 * Set @uchar to output an 8-bit unsigned char image rather than a
134 * float image. In this case, pixels are in the range [0 - 255].
135 *
136 * See also: vips_mask_ideal(), vips_mask_ideal_ring(),
137 * vips_mask_ideal_band(), vips_mask_butterworth(),
138 * vips_mask_butterworth_ring(), vips_mask_butterworth_band(),
139 * vips_mask_gaussian(), vips_mask_gaussian_ring(),
140 * vips_mask_gaussian_band().
141 *
142 * Returns: 0 on success, -1 on error
143 */
144 int
vips_mask_ideal(VipsImage ** out,int width,int height,double frequency_cutoff,...)145 vips_mask_ideal( VipsImage **out, int width, int height,
146 double frequency_cutoff, ... )
147 {
148 va_list ap;
149 int result;
150
151 va_start( ap, frequency_cutoff );
152 result = vips_call_split( "mask_ideal", ap, out, width, height,
153 frequency_cutoff );
154 va_end( ap );
155
156 return( result );
157 }
158