PhotometricInterpreterLogLuv.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.tiff.photometricinterpreters;
import java.io.IOException;
import org.apache.commons.imaging.ImagingException;
import org.apache.commons.imaging.common.ImageBuilder;
/**
* Photometric interpretation Logluv support. Logluv is an encoding for storing data inside TIFF images.
*
* @see <a href="https://en.wikipedia.org/wiki/Logluv_TIFF">Logluv TIFF</a>
*/
public class PhotometricInterpreterLogLuv extends PhotometricInterpreter {
/**
* Rgb values (reg-green-blue, as R-G-B, as in the RGB color model).
*/
static class RgbValues {
public int r;
public int g;
public int b;
}
/**
* Tristimulus color values (red-green-blue, as X-Y-Z, in the CIE XYZ color space).
*/
static class TristimulusValues {
public float x;
public float y;
public float z;
}
public PhotometricInterpreterLogLuv(final int samplesPerPixel, final int[] bitsPerSample, final int predictor, final int width, final int height) {
super(samplesPerPixel, bitsPerSample, predictor, width, height);
}
/**
* Receives a triplet tristimulus values (CIE XYZ) and then does a CIELAB-CIEXYZ conversion (consult Wikipedia link for formula), where the CIELAB values
* are used to calculate the tristimulus values of the reference white point.
*
* @param tristimulusValues the XYZ tristimulus values
* @return RGB values
* @see <a href="https://en.wikipedia.org/wiki/CIELAB_color_space">CIELAB color space</a>
*/
RgbValues getRgbValues(final TristimulusValues tristimulusValues) {
final float varX = tristimulusValues.x / 100f; // X = From 0 to ref_X
final float varY = tristimulusValues.y / 100f; // Y = From 0 to ref_Y
final float varZ = tristimulusValues.z / 100f; // Z = From 0 to ref_Y
float varR = varX * 3.2406f + varY * -1.5372f + varZ * -0.4986f;
float varG = varX * -0.9689f + varY * 1.8758f + varZ * 0.0415f;
float varB = varX * 0.0557f + varY * -0.2040f + varZ * 1.0570f;
if (varR > 0.0031308) {
varR = 1.055f * (float) Math.pow(varR, 1 / 2.4) - 0.055f;
} else {
varR = 12.92f * varR;
}
if (varG > 0.0031308) {
varG = 1.055f * (float) Math.pow(varG, 1 / 2.4) - 0.055f;
} else {
varG = 12.92f * varG;
}
if (varB > 0.0031308) {
varB = 1.055f * (float) Math.pow(varB, 1 / 2.4) - 0.055f;
} else {
varB = 12.92f * varB;
}
// var_R = ((var_R + 0.16561039f) / (3.0152583f + 0.16561039f));
// var_G = ((var_G + 0.06561642f) / (3.0239854f + 0.06561642f));
// var_B = ((var_B + 0.19393992f) / (3.1043448f + 0.19393992f));
final RgbValues values = new RgbValues();
values.r = (int) (varR * 255f);
values.g = (int) (varG * 255f);
values.b = (int) (varB * 255f);
return values;
}
/**
* Receives a triplet of CIELAB values, and calculates the tristimulus values. The reference white point used here is the equivalent to summer sun and sky.
*
* @param cieL lightness from black to white
* @param cieA lightness from green to red
* @param cieB lightness from blue to yellow
* @return tristimulus (X, Y, and Z) values
* @see <a href="https://en.wikipedia.org/wiki/CIELAB_color_space">CIELAB color space</a>
* @see <a href="https://en.wikipedia.org/wiki/White_point">White point</a>
*/
TristimulusValues getTristimulusValues(final int cieL, final int cieA, final int cieB) {
float varY = (cieL * 100.0f / 255.0f + 16.0f) / 116.0f;
float varX = cieA / 500.0f + varY;
float varZ = varY - cieB / 200.0f;
final float varXCube = (float) Math.pow(varX, 3.0d);
final float varYCube = (float) Math.pow(varY, 3.0d);
final float varZCube = (float) Math.pow(varZ, 3.0d);
if (varYCube > 0.008856f) {
varY = varYCube;
} else {
varY = (varY - 16 / 116.0f) / 7.787f;
}
if (varXCube > 0.008856f) {
varX = varXCube;
} else {
varX = (varX - 16 / 116.0f) / 7.787f;
}
if (varZCube > 0.008856f) {
varZ = varZCube;
} else {
varZ = (varZ - 16 / 116.0f) / 7.787f;
}
// These reference values are the relative white points (XYZ) for commons scene types.
// The chosen values here reflect a scene with Summer Sun and Sky, temperature of 6504 K,
// X 95.047, Y 100.0, and Z 108.883.
// See Color Science by Wyszecki and Stiles for more
final float refX = 95.047f;
final float refY = 100.000f;
final float refZ = 108.883f;
final TristimulusValues values = new TristimulusValues();
values.x = refX * varX; // ref_X = 95.047 Observer= 2°, Illuminant= D65
values.y = refY * varY; // ref_Y = 100.000
values.z = refZ * varZ; // ref_Z = 108.883
return values;
}
@Override
public void interpretPixel(final ImageBuilder imageBuilder, final int[] samples, final int x, final int y) throws ImagingException, IOException {
if (samples == null || samples.length != 3) {
throw new ImagingException("Invalid length of bits per sample (expected 3).");
}
// CIE illuminants. An illuminant is a theorical source of visible light with a profile.
// CIE stands for Commission Internationale de l'Eclairage, or International
// Comission on Illumination.
final int cieL = samples[0];
final int cieA = (byte) samples[1];
final int cieB = (byte) samples[2];
final TristimulusValues tristimulusValues = getTristimulusValues(cieL, cieA, cieB);
// ref_X = 95.047 //Observer = 2°, Illuminant = D65
// ref_Y = 100.000
// ref_Z = 108.883
final RgbValues rgbValues = getRgbValues(tristimulusValues);
// float R = 1.910f * X - 0.532f * Y - 0.288f * Z;
// float G = -0.985f * X + 1.999f * Y - 0.028f * Z;
// float B = 0.058f * X - 0.118f * Y + 0.898f * Z;
final int red = Math.min(255, Math.max(0, rgbValues.r));
final int green = Math.min(255, Math.max(0, rgbValues.g));
final int blue = Math.min(255, Math.max(0, rgbValues.b));
final int alpha = 0xff;
final int rgb = alpha << 24 | red << 16 | green << 8 | blue << 0;
imageBuilder.setRgb(x, y, rgb);
}
}