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 org.openimaj.image.processor.PixelProcessor;
033
034/**
035 * Class to perform Gamma correction on a grey-level image.
036 * Grey levels are transformed such that I_new = I^Gamma for
037 * Gamma > 0 and all pixels I. If Gamma == 0 then the transform
038 * is I_new = log(I). 
039 * 
040 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
041 *
042 */
043public class GammaCorrection implements PixelProcessor<Float> {
044        protected double gamma;
045        
046        /**
047         * Construct a GammaCorrection with the default gamma of 0.2
048         */
049        public GammaCorrection() {
050                this.gamma = 0.2; 
051        }
052        
053        /**
054         * Construct a GammaCorrection with the given gamma
055         * @param gamma The gamma value to use
056         */
057        public GammaCorrection(double gamma) {
058                this.gamma = gamma; 
059        }
060        
061        @Override
062        public Float processPixel(Float pixel) {
063                if (gamma == 0) {
064                        return (float) Math.log(pixel);
065                }
066                return (float) Math.pow(pixel, gamma);
067        }
068}
069