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.feature.local.descriptor.gradient;
031
032import org.openimaj.feature.OrientedFeatureVector;
033import org.openimaj.image.feature.local.descriptor.LocalFeatureProvider;
034import org.openimaj.math.util.Interpolation;
035
036
037/**
038 * Interface for classes capable of building local descriptors
039 * from the gradient (magnitude and orientation) information in
040 * an image patch. The model for the construction of various
041 * concrete feature extractors that implement this interface 
042 * is that some external code will provide individual pixel
043 * samples (consisting of both magnitude and orientation values)
044 * and their relative positions within a unit sampling patch (or
045 * slightly beyond if interpolation is used; see {@link Interpolation#bilerp }).  
046 * <br/><br/>
047 * The general contract for methods using this interface is
048 * as follows: <br/><br/>
049 * <code>
050 *      f = new GradientBasedLocalFeatureExtractorImpl() <br/>
051 *      f.setPatchOrientation(orientation) <br/>
052 *      for (pixels in patch) <br/>
053 *      &nbsp;&nbsp;&nbsp;&nbsp;f.addSample(normalised-pixel-position, pixel-magnitude, pixel-orientation) <br/>
054 * </code>
055 * 
056 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
057 *
058 */
059public interface GradientFeatureProvider extends LocalFeatureProvider<OrientedFeatureVector> {
060        /**
061         * Set the primary orientation of the sample patch in the image
062         * being processed. This might be used by concrete implementations
063         * to provide rotation invariance.
064         * 
065         * This method should only be called once by calling code, and the call
066         * should be before any calls to {@link #addSample(float, float, float, float)} 
067         * are made.
068         * 
069         * @param patchOrientation the actual orientation of the square in the image
070         */
071        public abstract void setPatchOrientation(float patchOrientation);
072        
073        /**
074         * Add a sample to the feature. The x and y coordinates are given
075         * in terms of a unit index square (i.e. 0<=x<=1 and 0<=y<=1).  
076         * 
077         * @param x x-coordinate within the unit indexing square
078         * @param y y-coordinate within the unit indexing square
079         * @param gradmag the gradient magnitude at the given coordinate
080         * @param gradori the gradient direction at the given coordinate
081         */
082        public abstract void addSample(float x, float y, float gradmag, float gradori);
083        
084        @Override
085        public OrientedFeatureVector getFeatureVector();
086}