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.edges;
31
32 import static java.lang.Math.atan;
33 import static java.lang.Math.sqrt;
34
35 import org.openimaj.image.FImage;
36 import org.openimaj.image.analyser.ImageAnalyser;
37
38 /**
39 * Using a simple sobel-like x and y derivative kernel, find edges in an image.
40 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
41 * @author Sina Samangooei (ss@ecs.soton.ac.uk)
42 *
43 */
44 public class EdgeFinder implements ImageAnalyser<FImage> {
45 protected float [][] kx;
46 protected float [][] ky;
47
48 /**
49 * The magnitudes of each edge as worked out by the hypotenuse of the triangle formed by the dx and dy of a pixel
50 */
51 public FImage magnitude;
52 /**
53 * The direction of each edge as worked out by the angle between the triangle formed by the dx and dy of a pixel
54 */
55 public FImage angle;
56
57 /**
58 * Find edges in an image using the following edge kernels
59 * @param kx
60 * @param ky
61 */
62 public EdgeFinder(float [][] kx, float [][] ky) {
63 this.kx = kx;
64 this.ky = ky;
65 }
66
67 /**
68 * Find the edges in an image using default, sobel like 5x5 derivative kernels
69 */
70 public EdgeFinder() {
71 kx = new float[][] {
72 {+1, +1, 0, -1, -1},
73 {+2, +2, 0, -2, -2},
74 {+2, +2, 0, -2, -2},
75 {+2, +2, 0, -2, -2},
76 {+1, +1, 0, -1, -1}
77 };
78
79 ky = new float[][] {
80 {+1, +2, +2, +2, +1},
81 {+1, +2, +2, +2, +1},
82 { 0, 0, 0, 0, 0},
83 {-1, -2, -2, -2, -1},
84 {-1, -2, -2, -2, -1}
85 };
86 }
87
88 /* (non-Javadoc)
89 * @see org.openimaj.image.processor.ImageProcessor#processImage(org.openimaj.image.Image)
90 */
91 @Override
92 public void analyseImage(FImage image) {
93 int height = image.getHeight();
94 int width = image.getWidth();
95
96 magnitude = new FImage(width, height);
97 angle = new FImage(width, height);
98
99 int w = (kx.length - 1) / 2;
100
101 for (int y=w+1; y<height-w; y++) {
102 for (int x=w+1; x<width-w; x++) {
103 //compute gradient
104 double gx = 0;
105 double gy = 0;
106 for (int j=0; j<kx.length; j++) {
107 for (int i=0; i<kx.length; i++) {
108 gx += image.pixels[y-w+j][x-w+i] * kx[j][i];
109 gy += image.pixels[y-w+j][x-w+i] * ky[j][i];
110 }
111 }
112
113 magnitude.pixels[y][x] = (float) sqrt(gx*gx + gy*gy);
114
115 if(gy!=0)
116 angle.pixels[y][x] = (float) atan(gx/-gy);
117 else
118 angle.pixels[y][x] = 1.57f;
119 }
120 }
121 }
122 }