1 /**
2 * Copyright (c) 2011, The University of Southampton and the individual contributors.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without modification,
6 * are permitted provided that the following conditions are met:
7 *
8 * * Redistributions of source code must retain the above copyright notice,
9 * this list of conditions and the following disclaimer.
10 *
11 * * Redistributions in binary form must reproduce the above copyright notice,
12 * this list of conditions and the following disclaimer in the documentation
13 * and/or other materials provided with the distribution.
14 *
15 * * Neither the name of the University of Southampton nor the names of its
16 * contributors may be used to endorse or promote products derived from this
17 * software without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
21 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
22 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
23 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
24 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
25 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
26 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
28 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30 package org.openimaj.image.processing.convolution;
31
32 import org.openimaj.image.FImage;
33 import org.openimaj.math.util.FloatArrayStatsUtils;
34
35 /**
36 * Disk - a circular averaging filter.
37 *
38 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
39 *
40 */
41 public class Disk extends FConvolution {
42
43 /**
44 * Default constructor. Makes a disk averaging filter
45 * with the given radius.
46 * @param radius the radius.
47 */
48 public Disk(int radius) {
49 super(createKernelImage(radius));
50 }
51
52 /**
53 * Makes a disk averaging filter with the given radius.
54 * @param radius
55 * @return the filter image
56 */
57 public static FImage createKernelImage(int radius) {
58 int sze = 2*radius+1;
59 FImage f = new FImage(sze, sze);
60 int hsz = (sze-1)/2;
61
62 for (int y=-hsz, j=0; y<hsz; y++, j++) {
63 for (int x=-hsz, i=0; x<hsz; x++, i++) {
64 double rad = Math.sqrt(x*x + y*y);
65 f.pixels[j][i] = rad < radius ? 1 : 0;
66 }
67 }
68 float sum = FloatArrayStatsUtils.sum(f.pixels);
69 return f.divideInplace(sum);
70 }
71 }