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.analysis.algorithm.histogram;
31
32 import org.openimaj.image.FImage;
33 import org.openimaj.image.analysis.algorithm.SummedAreaTable;
34 import org.openimaj.math.geometry.shape.Rectangle;
35 import org.openimaj.math.statistics.distribution.Histogram;
36
37 /**
38 * This class implements a {@link WindowedHistogramExtractor} with the primary
39 * purpose of of producing efficient access to histograms of arbitrary windows
40 * of the image.
41 * <p>
42 * This implementation is based on a stack of {@link SummedAreaTable}s, with one
43 * {@link SummedAreaTable} per histogram bin. Obviously this is quite memory
44 * intensive, so should probably only be used with small numbers of bins.
45 * However, the advantage over a {@link BinnedWindowedExtractor} is that the
46 * histogram extraction is an O(1) operation, and it is thus very quick for
47 * evaluating many windows.
48 *
49 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
50 */
51 public class SATWindowedExtractor implements WindowedHistogramExtractor {
52 protected final SummedAreaTable[] sats;
53 protected final int nbins;
54
55 /**
56 * Protected constructor for subclasses to use if they don't wan't to
57 * compute the SATs at construction time
58 *
59 * @param nbins
60 * the number of histogram bins.
61 */
62 protected SATWindowedExtractor(int nbins) {
63 this.nbins = nbins;
64 this.sats = new SummedAreaTable[nbins];
65 }
66
67 /**
68 * Construct with the given spatial histogram magnitude maps. Each image
69 * represents a bin of the histogram, and each element is the histogram
70 * weight at the respective spatial location for the corresponding bin
71 * (usually the images will be very sparse).
72 *
73 * @param magnitudeMaps
74 * array of images, one per bin, with each pixel set to the
75 * histogram magnitude at that bin
76 */
77 public SATWindowedExtractor(FImage[] magnitudeMaps) {
78 this.nbins = magnitudeMaps.length;
79
80 sats = new SummedAreaTable[nbins];
81 computeSATs(magnitudeMaps);
82 }
83
84 protected void computeSATs(FImage[] magnitudeMaps) {
85 for (int i = 0; i < nbins; i++) {
86 sats[i] = new SummedAreaTable(magnitudeMaps[i]);
87 }
88 }
89
90 /*
91 * (non-Javadoc)
92 *
93 * @see
94 * org.openimaj.image.analysis.algorithm.ImageHistogramAnalyser#getNumBins()
95 */
96 @Override
97 public int getNumBins() {
98 return nbins;
99 }
100
101 /*
102 * (non-Javadoc)
103 *
104 * @see
105 * org.openimaj.image.analysis.algorithm.ImageHistogramAnalyser#computeHistogram
106 * (org.openimaj.math.geometry.shape.Rectangle)
107 */
108 @Override
109 public Histogram computeHistogram(Rectangle roi) {
110 return computeHistogram((int) roi.x, (int) roi.y, (int) roi.width, (int) roi.height);
111 }
112
113 /*
114 * (non-Javadoc)
115 *
116 * @see
117 * org.openimaj.image.analysis.algorithm.ImageHistogramAnalyser#computeHistogram
118 * (int, int, int, int)
119 */
120 @Override
121 public Histogram computeHistogram(final int x, final int y, final int w, final int h) {
122 final Histogram hist = new Histogram(nbins);
123 final int x2 = x + w;
124 final int y2 = y + h;
125
126 for (int i = 0; i < nbins; i++) {
127 final float val = sats[i].calculateArea(x, y, x2, y2);
128 // rounding errors in the SAT can lead to small values that should
129 // actually be zero
130 hist.values[i] = val < 1e-4 ? 0 : val;
131
132 }
133
134 return hist;
135 }
136
137 @Override
138 public void computeHistogram(final int x, final int y, final int w, final int h, final Histogram hist) {
139 final int x2 = x + w;
140 final int y2 = y + h;
141 final double[] values = hist.values;
142
143 for (int i = 0; i < values.length; i++) {
144 final float val = sats[i].calculateArea(x, y, x2, y2);
145 values[i] = Math.max(0, val); // rounding errors in the SAT
146 // might lead to small -ve's
147 }
148 }
149
150 @Override
151 public void computeHistogram(Rectangle roi, Histogram histogram) {
152 computeHistogram((int) roi.x, (int) roi.y, (int) roi.width, (int) roi.height, histogram);
153 }
154 }