001/**
002 * Copyright (c) 2011, The University of Southampton and the individual contributors.
003 * All rights reserved.
004 *
005 * Redistribution and use in source and binary forms, with or without modification,
006 * are permitted provided that the following conditions are met:
007 *
008 *   *  Redistributions of source code must retain the above copyright notice,
009 *      this list of conditions and the following disclaimer.
010 *
011 *   *  Redistributions in binary form must reproduce the above copyright notice,
012 *      this list of conditions and the following disclaimer in the documentation
013 *      and/or other materials provided with the distribution.
014 *
015 *   *  Neither the name of the University of Southampton nor the names of its
016 *      contributors may be used to endorse or promote products derived from this
017 *      software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
020 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
021 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
022 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
023 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
026 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
028 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030package org.openimaj.image.analysis.algorithm.histogram;
031
032import org.openimaj.image.FImage;
033import org.openimaj.image.analyser.ImageAnalyser;
034import org.openimaj.image.processor.ImageProcessor;
035import org.openimaj.math.statistics.distribution.Histogram;
036
037/**
038 * An {@link ImageAnalyser} that processes an image and generates a
039 * {@link Histogram}.
040 * <p>
041 * You can get the histogram for an image like so: <code><pre>
042 *      {@code
043 *              FImage img = new FImage( ... );
044 *              HistogramProcessor hp = new HistogramProcessor( 64 );
045 *              img.analyse( hp );
046 *              Histogram h = hp.getHistogram();
047 *      }
048 *      </pre></code>
049 *  </p>
050 *
051 * @see FImage#process(ImageProcessor)
052 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
053 */
054public class HistogramAnalyser implements ImageAnalyser<FImage>
055{
056        /** The number of bins in the histogram */
057        private int nbins;
058
059        /** The histogram being built */
060        private Histogram histogram;
061
062        /**
063         * Default constructor that builds a histogram processor that will create
064         * histograms with the given number of bins.
065         *
066         * @param nbins
067         *            The number of bins.
068         */
069        public HistogramAnalyser(int nbins) {
070                this.nbins = nbins;
071        }
072
073        /**
074         * Computes the Histogram for this image. The assumption is that the image
075         * has been normalised to the range 0..1. Values greater than 1 will be
076         * placed in the top bin.
077         *
078         * @param image
079         *            The image from which to extract histogram
080         */
081        @Override
082        public void analyseImage(FImage image) {
083                this.histogram = new Histogram(nbins);
084                for (int r = 0; r < image.height; r++)
085                {
086                        for (int c = 0; c < image.width; c++)
087                        {
088                                int bin = (int) (image.pixels[r][c] * nbins);
089                                if (bin > (nbins - 1))
090                                        bin = nbins - 1;
091                                histogram.values[bin]++;
092                        }
093                }
094        }
095
096        /**
097         * Returns the histogram that was built having run the processing function.
098         * This will return null if the processing has not yet been run.
099         *
100         * @return The {@link Histogram} that was built.
101         */
102        public Histogram getHistogram()
103        {
104                return histogram;
105        }
106
107        /**
108         * Quickly create a histogram from an image.
109         *
110         * @param image
111         *            the image
112         * @param nbins
113         *            the number of bins per band
114         * @return a histogram
115         */
116        public static Histogram getHistogram(FImage image, int nbins) {
117                final HistogramAnalyser p = new HistogramAnalyser(nbins);
118                image.analyseWith(p);
119                return p.getHistogram();
120        }
121}