/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.commons.imaging.formats.png;
  
  import java.util.logging.Level;
  import java.util.logging.Logger;
  
  public class GammaCorrection {
  
      private static final Logger LOGGER = Logger.getLogger(GammaCorrection.class.getName());
  
      private final int[] lookupTable;
  
      public GammaCorrection(final double srcGamma, final double dstGamma) {
  
          if (LOGGER.isLoggable(Level.FINEST)) {
              LOGGER.finest("srcGamma: " + srcGamma);
              LOGGER.finest("dstGamma: " + dstGamma);
          }
  
          lookupTable = new int[256];
          for (int i = 0; i < 256; i++) {
              lookupTable[i] = correctSample(i, srcGamma, dstGamma);
              if (LOGGER.isLoggable(Level.FINEST)) {
                  LOGGER.finest("lookupTable[" + i + "]: " + lookupTable[i]);
              }
          }
      }
  
      public int correctArgb(final int pixel) {
          final int alpha = 0xff000000 & pixel;
          int red = pixel >> 16 & 0xff;
          int green = pixel >> 8 & 0xff;
          int blue = pixel >> 0 & 0xff;
  
          red = correctSample(red);
          green = correctSample(green);
          blue = correctSample(blue);
  
          return alpha | (0xff & red) << 16 | (0xff & green) << 8 | (0xff & blue) << 0;
      }
  
      public int correctSample(final int sample) {
          return lookupTable[sample];
      }
  
      private int correctSample(final int sample, final double srcGamma, final double dstGamma) {
          // if (kUseAdobeGammaMethod && val <= 32)
          // {
          // double slope = Math.round(255.0d * Math.pow((32.0 / 255.0d),
          // src_gamma / dst_gamma)) / 32.d;
          // return (int) (sample * slope);
          // }
  
          return (int) Math.round(255.0d * Math.pow(sample / 255.0d, srcGamma / dstGamma));
      }
  
  }