001/*
002 * $RCSfile: TIFFCIELabColorConverter.java,v $
003 *
004 * 
005 * Copyright (c) 2005 Sun Microsystems, Inc. All  Rights Reserved.
006 * 
007 * Redistribution and use in source and binary forms, with or without
008 * modification, are permitted provided that the following conditions
009 * are met: 
010 * 
011 * - Redistribution of source code must retain the above copyright 
012 *   notice, this  list of conditions and the following disclaimer.
013 * 
014 * - Redistribution in binary form must reproduce the above copyright
015 *   notice, this list of conditions and the following disclaimer in 
016 *   the documentation and/or other materials provided with the
017 *   distribution.
018 * 
019 * Neither the name of Sun Microsystems, Inc. or the names of 
020 * contributors may be used to endorse or promote products derived 
021 * from this software without specific prior written permission.
022 * 
023 * This software is provided "AS IS," without a warranty of any 
024 * kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND 
025 * WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, 
026 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY
027 * EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN") AND ITS LICENSORS SHALL 
028 * NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF 
029 * USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
030 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR 
031 * ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL,
032 * CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND
033 * REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF THE USE OF OR
034 * INABILITY TO USE THIS SOFTWARE, EVEN IF SUN HAS BEEN ADVISED OF THE
035 * POSSIBILITY OF SUCH DAMAGES. 
036 * 
037 * You acknowledge that this software is not designed or intended for 
038 * use in the design, construction, operation or maintenance of any 
039 * nuclear facility. 
040 *
041 * $Revision: 1.1 $
042 * $Date: 2005/02/11 05:01:44 $
043 * $State: Exp $
044 */
045package com.github.jaiimageio.impl.plugins.tiff;
046
047import com.github.jaiimageio.plugins.tiff.TIFFColorConverter;
048
049/**
050 */
051public class TIFFCIELabColorConverter extends TIFFColorConverter {
052
053    // XYX coordinate or reference white (CIE D65)
054    private static final float Xn = 95.047f;
055    private static final float Yn = 100.0f;
056    private static final float Zn = 108.883f;
057
058    private static final float THRESHOLD = (float)Math.pow(0.008856, 1.0/3.0);
059
060    public TIFFCIELabColorConverter() {}
061
062
063    private float clamp(float x) {
064        if (x < 0.0f) {
065            return 0.0f;
066        } else if (x > 100.0f) {
067            return 255.0f;
068        } else {
069            return x*(255.0f/100.0f);
070        }
071    }
072
073    private float clamp2(float x) {
074        if (x < 0.0f) {
075            return 0.0f;
076        } else if (x > 255.0f) {
077            return 255.0f;
078        } else {
079            return x;
080        }
081    }
082
083    public void fromRGB(float r, float g, float b, float[] result) {
084        float X =  0.412453f*r + 0.357580f*g + 0.180423f*b;
085        float Y =  0.212671f*r + 0.715160f*g + 0.072169f*b;
086        float Z =  0.019334f*r + 0.119193f*g + 0.950227f*b;
087
088        float YYn = Y/Yn;
089        float XXn = X/Xn;
090        float ZZn = Z/Zn;
091
092        if (YYn < 0.008856f) {
093            YYn = 7.787f*YYn + 16.0f/116.0f;
094        } else {
095            YYn = (float)Math.pow(YYn, 1.0/3.0);
096        }
097        
098        if (XXn < 0.008856f) {
099            XXn = 7.787f*XXn + 16.0f/116.0f;
100        } else {
101            XXn = (float)Math.pow(XXn, 1.0/3.0);
102        }
103        
104        if (ZZn < 0.008856f) {
105            ZZn = 7.787f*ZZn + 16.0f/116.0f;
106        } else {
107            ZZn = (float)Math.pow(ZZn, 1.0/3.0);
108        }
109        
110        float LStar = 116.0f*YYn - 16.0f;
111        float aStar = 500.0f*(XXn - YYn);
112        float bStar = 200.0f*(YYn - ZZn);
113
114        LStar *= 255.0f/100.0f;
115        if (aStar < 0.0f) {
116            aStar += 256.0f;
117        }
118        if (bStar < 0.0f) {
119            bStar += 256.0f;
120        }
121
122        result[0] = clamp2(LStar);
123        result[1] = clamp2(aStar);
124        result[2] = clamp2(bStar);
125    }
126
127    public void toRGB(float x0, float x1, float x2, float[] rgb) {
128        float LStar = x0*100.0f/255.0f;
129        float aStar = (x1 > 128.0f) ? (x1 - 256.0f) : x1;
130        float bStar = (x2 > 128.0f) ? (x2 - 256.0f) : x2;
131
132        float YYn; // Y/Yn
133        float fY; // 'F' value for Y
134        
135        if (LStar < 8.0f) {
136            YYn = LStar/903.3f;
137            fY = 7.787f*YYn + 16.0f/116.0f;
138        } else {
139            float YYn_cubeRoot = (LStar + 16.0f)/116.0f;
140            YYn = YYn_cubeRoot*YYn_cubeRoot*YYn_cubeRoot;
141            fY = (float)Math.pow(YYn, 1.0/3.0);
142        }
143        float Y = YYn*Yn;
144        
145        float fX = fY + (aStar/500.0f);
146        float X;
147        if (fX <= THRESHOLD) {
148            X = Xn*(fX - 16.0f/116.0f)/7.787f;
149        } else {
150            X = Xn*fX*fX*fX;
151        }
152        
153        float fZ = fY - bStar/200.0f;
154        float Z;
155        if (fZ <= THRESHOLD) {
156            Z = Zn*(fZ - 16.0f/116.0f)/7.787f;
157        } else {
158            Z = Zn*fZ*fZ*fZ;
159        }
160
161        float R =  3.240479f*X - 1.537150f*Y - 0.498535f*Z;
162        float G = -0.969256f*X + 1.875992f*Y + 0.041556f*Z;
163        float B =  0.055648f*X - 0.204043f*Y + 1.057311f*Z;
164
165        rgb[0] = clamp(R);
166        rgb[1] = clamp(G);
167        rgb[2] = clamp(B);
168    }
169}