    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.imaging.formats.png;
    018
    019import java.util.logging.Level;
    020import java.util.logging.Logger;
    021
    022public class GammaCorrection {
    023
    024    private static final Logger LOGGER = Logger.getLogger(GammaCorrection.class.getName());
    025
    026    private final int[] lookupTable;
    027
    028    public GammaCorrection(final double srcGamma, final double dstGamma) {
    029
    030        if (LOGGER.isLoggable(Level.FINEST)) {
    031            LOGGER.finest("srcGamma: " + srcGamma);
    032            LOGGER.finest("dstGamma: " + dstGamma);
    033        }
    034
    035        lookupTable = new int[256];
    036        for (int i = 0; i < 256; i++) {
    037            lookupTable[i] = correctSample(i, srcGamma, dstGamma);
    038            if (LOGGER.isLoggable(Level.FINEST)) {
    039                LOGGER.finest("lookupTable[" + i + "]: " + lookupTable[i]);
    040            }
    041        }
    042    }
    043
    044    public int correctArgb(final int pixel) {
    045        final int alpha = 0xff000000 & pixel;
    046        int red = pixel >> 16 & 0xff;
    047        int green = pixel >> 8 & 0xff;
    048        int blue = pixel >> 0 & 0xff;
    049
    050        red = correctSample(red);
    051        green = correctSample(green);
    052        blue = correctSample(blue);
    053
    054        return alpha | (0xff & red) << 16 | (0xff & green) << 8 | (0xff & blue) << 0;
    055    }
    056
    057    public int correctSample(final int sample) {
    058        return lookupTable[sample];
    059    }
    060
    061    private int correctSample(final int sample, final double srcGamma, final double dstGamma) {
    062        // if (kUseAdobeGammaMethod && val <= 32)
    063        // {
    064        // double slope = Math.round(255.0d * Math.pow((32.0 / 255.0d),
    065        // src_gamma / dst_gamma)) / 32.d;
    066        // return (int) (sample * slope);
    067        // }
    068
    069        return (int) Math.round(255.0d * Math.pow(sample / 255.0d, srcGamma / dstGamma));
    070    }
    071
    072}