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}