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.tiff.photometricinterpreters;
018
019import java.io.IOException;
020
021import org.apache.commons.imaging.ImageReadException;
022import org.apache.commons.imaging.common.ImageBuilder;
023
024/**
025 * Photometric interpretation Logluv support. Logluv is an encoding for storing
026 * data inside TIFF images.
027 *
028 * @see <a href="https://en.wikipedia.org/wiki/Logluv_TIFF">Logluv TIFF</a>
029 */
030public class PhotometricInterpreterLogLuv extends PhotometricInterpreter {
031
032    /**
033     * Tristimulus color values (red-green-blue, as X-Y-Z, in the CIE XYZ color space).
034     */
035    static class TristimulusValues {
036        public float x;
037        public float y;
038        public float z;
039    }
040
041    /**
042     * Rgb values (reg-green-blue, as R-G-B, as in the RGB color model).
043     */
044    static class RgbValues {
045        public int r;
046        public int g;
047        public int b;
048    }
049
050    public PhotometricInterpreterLogLuv(final int samplesPerPixel,
051            final int[] bitsPerSample, final int predictor, final int width, final int height) {
052        super(samplesPerPixel, bitsPerSample, predictor, width, height);
053    }
054
055    @Override
056    public void interpretPixel(final ImageBuilder imageBuilder, final int[] samples, final int x,
057            final int y) throws ImageReadException, IOException {
058        if (samples == null || samples.length != 3) {
059            throw new ImageReadException("Invalid length of bits per sample (expected 3).");
060        }
061
062        // CIE illuminants. An illuminant is a theorical source of visible light with a profile.
063        // CIE stands for Commission Internationale de l'Eclairage, or International
064        // Comission on Illumination.
065        final int cieL = samples[0];
066        final int cieA = (byte) samples[1];
067        final int cieB = (byte) samples[2];
068
069        final TristimulusValues tristimulusValues = getTristimulusValues(cieL, cieA, cieB);
070
071        // ref_X = 95.047 //Observer = 2°, Illuminant = D65
072        // ref_Y = 100.000
073        // ref_Z = 108.883
074
075        final RgbValues rgbValues = getRgbValues(tristimulusValues);
076
077        // float R = 1.910f * X - 0.532f * Y - 0.288f * Z;
078        // float G = -0.985f * X + 1.999f * Y - 0.028f * Z;
079        // float B = 0.058f * X - 0.118f * Y + 0.898f * Z;
080
081        final int red = Math.min(255, Math.max(0, rgbValues.r));
082        final int green = Math.min(255, Math.max(0, rgbValues.g));
083        final int blue = Math.min(255, Math.max(0, rgbValues.b));
084        final int alpha = 0xff;
085        final int rgb = (alpha << 24) | (red << 16) | (green << 8) | (blue << 0);
086        imageBuilder.setRGB(x, y, rgb);
087
088    }
089
090    /**
091     * Receives a triplet of CIELAB values, and calculates the tristimulus values.
092     * The reference white point used here is the equivalent to summer sun and sky.
093     *
094     * @param cieL lightness from black to white
095     * @param cieA lightness from green to red
096     * @param cieB lightness from blue to yellow
097     * @return tristimulus (X, Y, and Z) values
098     * @see <a href="https://en.wikipedia.org/wiki/CIELAB_color_space">CIELAB color space</a>
099     * @see <a href="https://en.wikipedia.org/wiki/White_point">White point</a>
100     */
101    TristimulusValues getTristimulusValues(int cieL, int cieA, int cieB) {
102        float var_Y = ((cieL * 100.0f / 255.0f) + 16.0f) / 116.0f;
103        float var_X = cieA / 500.0f + var_Y;
104        float var_Z = var_Y - cieB / 200.0f;
105
106        final float var_x_cube = (float) Math.pow(var_X, 3.0d);
107        final float var_y_cube = (float) Math.pow(var_Y, 3.0d);
108        final float var_z_cube = (float) Math.pow(var_Z, 3.0d);
109
110        if (var_y_cube > 0.008856f) {
111            var_Y = var_y_cube;
112        } else {
113            var_Y = (var_Y - 16 / 116.0f) / 7.787f;
114        }
115
116        if (var_x_cube > 0.008856f) {
117            var_X = var_x_cube;
118        } else {
119            var_X = (var_X - 16 / 116.0f) / 7.787f;
120        }
121
122        if (var_z_cube > 0.008856f) {
123            var_Z = var_z_cube;
124        } else {
125            var_Z = (var_Z - 16 / 116.0f) / 7.787f;
126        }
127
128        // These reference values are the relative white points (XYZ) for commons scene types.
129        // The chosen values here reflect a scene with Summer Sun and Sky, temperature of 6504 K,
130        // X 95.047, Y 100.0, and Z 108.883.
131        // See Color Science by Wyszecki and Stiles for more
132        final float ref_X = 95.047f;
133        final float ref_Y = 100.000f;
134        final float ref_Z = 108.883f;
135
136        final TristimulusValues values = new TristimulusValues();
137        values.x = ref_X * var_X; // ref_X = 95.047 Observer= 2°, Illuminant= D65
138        values.y = ref_Y * var_Y; // ref_Y = 100.000
139        values.z = ref_Z * var_Z; // ref_Z = 108.883
140        return values;
141    }
142
143    /**
144     * Receives a triplet tristimulus values (CIE XYZ) and then does a CIELAB-CIEXYZ
145     * conversion (consult Wikipedia link for formula), where the CIELAB values are
146     * used to calculate the tristimulus values of the reference white point.
147     *
148     * @param tristimulusValues the XYZ tristimulus values
149     * @return RGB values
150     * @see <a href="https://en.wikipedia.org/wiki/CIELAB_color_space">CIELAB color space</a>
151     */
152    RgbValues getRgbValues(TristimulusValues tristimulusValues) {
153        final float var_X = tristimulusValues.x / 100f; // X = From 0 to ref_X
154        final float var_Y = tristimulusValues.y / 100f; // Y = From 0 to ref_Y
155        final float var_Z = tristimulusValues.z / 100f; // Z = From 0 to ref_Y
156
157        float var_R = var_X * 3.2406f + var_Y * -1.5372f + var_Z * -0.4986f;
158        float var_G = var_X * -0.9689f + var_Y * 1.8758f + var_Z * 0.0415f;
159        float var_B = var_X * 0.0557f + var_Y * -0.2040f + var_Z * 1.0570f;
160
161        if (var_R > 0.0031308) {
162            var_R = 1.055f * (float) Math.pow(var_R, (1 / 2.4)) - 0.055f;
163        } else {
164            var_R = 12.92f * var_R;
165        }
166        if (var_G > 0.0031308) {
167            var_G = 1.055f * (float) Math.pow(var_G, (1 / 2.4)) - 0.055f;
168        } else {
169            var_G = 12.92f * var_G;
170        }
171
172        if (var_B > 0.0031308) {
173            var_B = 1.055f * (float) Math.pow(var_B, (1 / 2.4)) - 0.055f;
174        } else {
175            var_B = 12.92f * var_B;
176        }
177
178        // var_R = ((var_R + 0.16561039f) / (3.0152583f + 0.16561039f));
179        // var_G = ((var_G + 0.06561642f) / (3.0239854f + 0.06561642f));
180        // var_B = ((var_B + 0.19393992f) / (3.1043448f + 0.19393992f));
181
182        final RgbValues values = new RgbValues();
183        values.r = (int) (var_R * 255f);
184        values.g = (int) (var_G * 255f);
185        values.b = (int) (var_B * 255f);
186        return values;
187    }
188}