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.math.geometry.transforms.check;
031
032import org.openimaj.math.geometry.point.Point2d;
033import org.openimaj.math.geometry.transforms.MatrixTransformProvider;
034import org.openimaj.math.model.Model;
035import org.openimaj.util.function.Predicate;
036
037import Jama.Matrix;
038
039/**
040 * Test whether a given model that produces a homogenous transform is
041 * orientation preserving
042 * 
043 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
044 * 
045 * @param <M>
046 */
047public class OrientationCheck2D<M extends Model<Point2d, Point2d> & MatrixTransformProvider> implements Predicate<M> {
048
049        @Override
050        public boolean test(M model) {
051                final Matrix H = model.getTransform();
052
053                // Hartley & Zisserman MVG:
054                // If the determinant of the top-left 2x2 matrix is > 0 the
055                // transformation is orientation-preserving.
056                // Else if the determinant is < 0, it is orientation-reversing.
057                final double det = H.get(0, 0) * H.get(1, 1) - H.get(1, 0) * H.get(0, 1);
058                if (det < 0)
059                        return false;
060
061                return true;
062        }
063}