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.processing.algorithm;
031
032import java.util.HashSet;
033import java.util.Set;
034
035import org.openimaj.image.pixel.ConnectedComponent;
036import org.openimaj.image.pixel.Pixel;
037
038/**
039 * Methods and statically defined templates for defining the support of local
040 * image filters.
041 * 
042 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
043 */
044public class FilterSupport {
045
046        /**
047         * Offsets for using a 3x3 cross shaped mask to select pixels for computing
048         * median.
049         */
050        public static final Set<Pixel> CROSS_3x3 = new HashSet<Pixel>();
051        static {
052                CROSS_3x3.add(new Pixel(0, -1));
053                CROSS_3x3.add(new Pixel(-1, 0));
054                CROSS_3x3.add(new Pixel(0, 0));
055                CROSS_3x3.add(new Pixel(1, 0));
056                CROSS_3x3.add(new Pixel(0, 1));
057        }
058
059        /**
060         * Offsets for using a 3x3 blocked shaped mask to select pixels for
061         * computing median.
062         */
063        public static final Set<Pixel> BLOCK_3x3 = createBlockSupport(3, 3);
064
065        /**
066         * Create a a rectangular support.
067         * 
068         * @param width
069         *            the width of the support
070         * @param height
071         *            the height of the support
072         * @return the support
073         */
074        public static final Set<Pixel> createBlockSupport(final int width, final int height) {
075                final HashSet<Pixel> indices = new HashSet<Pixel>(width * height);
076
077                final int startX = -width / 2;
078                final int startY = -height / 2;
079
080                for (int y = 0; y < height; y++) {
081                        for (int x = 0; x < width; x++) {
082                                indices.add(new Pixel(startX + x, startY + y));
083                        }
084                }
085
086                return indices;
087        }
088
089        /**
090         * Test whether the given support is a centred block
091         * 
092         * @param support
093         *            the support
094         * @return true if block, false otherwise
095         */
096        public final static boolean isBlockSupport(final Set<Pixel> support) {
097                final int sw = getSupportWidth(support);
098                final int sh = getSupportHeight(support);
099
100                return sw * sh == support.size() && isCentred(support);
101        }
102
103        private static boolean isCentred(Set<Pixel> support) {
104                final ConnectedComponent cc = new ConnectedComponent(support);
105                final Pixel cp = cc.calculateCentroidPixel();
106                return cp.x == 0 && cp.y == 0;
107        }
108
109        /**
110         * Get the width of the support region
111         * 
112         * @param support
113         *            the region
114         * @return the width
115         */
116        public final static int getSupportWidth(final Set<Pixel> support) {
117                int min = Integer.MAX_VALUE;
118                int max = -Integer.MAX_VALUE;
119
120                for (final Pixel p : support) {
121                        min = Math.min(min, p.x);
122                        max = Math.max(max, p.x);
123                }
124
125                return max - min + 1;
126        }
127
128        /**
129         * Get the height of the support region
130         * 
131         * @param support
132         *            the region
133         * @return the height
134         */
135        public final static int getSupportHeight(final Set<Pixel> support) {
136                int min = Integer.MAX_VALUE;
137                int max = -Integer.MAX_VALUE;
138
139                for (final Pixel p : support) {
140                        min = Math.min(min, p.y);
141                        max = Math.max(max, p.y);
142                }
143
144                return max - min + 1;
145        }
146}