GammaCorrection.java
/*
* 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));
}
}