1
/* SrgbConverter.java -- sRGB conversion class
2
Copyright (C) 2004 Free Software Foundation
4
This file is part of GNU Classpath.
6
GNU Classpath is free software; you can redistribute it and/or modify
7
it under the terms of the GNU General Public License as published by
8
the Free Software Foundation; either version 2, or (at your option)
11
GNU Classpath is distributed in the hope that it will be useful, but
12
WITHOUT ANY WARRANTY; without even the implied warranty of
13
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14
General Public License for more details.
16
You should have received a copy of the GNU General Public License
17
along with GNU Classpath; see the file COPYING. If not, write to the
18
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
21
Linking this library statically or dynamically with other modules is
22
making a combined work based on this library. Thus, the terms and
23
conditions of the GNU General Public License cover the whole
26
As a special exception, the copyright holders of this library give you
27
permission to link this library with independent modules to produce an
28
executable, regardless of the license terms of these independent
29
modules, and to copy and distribute the resulting executable under
30
terms of your choice, provided that you also meet, for each linked
31
independent module, the terms and conditions of the license of that
32
module. An independent module is a module which is not derived from
33
or based on this library. If you modify this library, you may extend
34
this exception to your version of the library, but you are not
35
obligated to do so. If you do not wish to do so, delete this
36
exception statement from your version. */
38
package gnu.java.awt.color;
42
* SrgbConverter - conversion routines for the sRGB colorspace
43
* sRGB is a standard for RGB colorspaces, adopted by the w3c.
45
* The specification is available at:
46
* http://www.w3.org/Graphics/Color/sRGB.html
48
* @author Sven de Marothy
52
* Note the matrix numbers used here are NOT identical to those in the
53
* w3 spec, as those numbers are CIE XYZ relative a D65 white point.
54
* The CIE XYZ we use is relative a D50 white point, so therefore a
55
* linear Bradford transform matrix for D65->D50 mapping has been applied.
56
* (The ICC documents describe this transform)
58
* Linearized Bradford transform:
59
* 0.8951 0.2664 -0.1614
60
* -0.7502 1.7135 0.0367
61
* 0.0389 -0.0685 1.0296
64
* 0.9870 -0.1471 0.1600
65
* 0.4323 0.5184 0.0493
66
* -0.00853 0.0400 0.9685
68
public class SrgbConverter implements ColorSpaceConverter
70
public float[] fromCIEXYZ(float[] in)
75
public float[] toCIEXYZ(float[] in)
80
public float[] toRGB(float[] in)
82
float[] out = new float[3];
83
System.arraycopy(in, 0, out, 0, 3);
87
public float[] fromRGB(float[] in)
89
float[] out = new float[3];
90
System.arraycopy(in, 0, out, 0, 3);
95
* CIE XYZ (D50 relative) --> sRGB
97
* Static as it's used by other ColorSpaceConverters to
98
* convert to sRGB if the color space is defined in XYZ.
100
public static float[] XYZtoRGB(float[] in)
102
float[] temp = new float[3];
103
temp[0] = 3.1338f * in[0] - 1.6171f * in[1] - 0.4907f * in[2];
104
temp[1] = -0.9785f * in[0] + 1.9160f * in[1] + 0.0334f * in[2];
105
temp[2] = 0.0720f * in[0] - 0.2290f * in[1] + 1.4056f * in[2];
107
float[] out = new float[3];
108
for (int i = 0; i < 3; i++)
114
if (temp[i] <= 0.00304f)
115
out[i] = temp[i] * 12.92f;
117
out[i] = 1.055f * ((float) Math.exp((1 / 2.4) * Math.log(temp[i])))
124
* sRGB --> CIE XYZ (D50 relative)
126
* Static as it's used by other ColorSpaceConverters to
127
* convert to XYZ if the color space is defined in RGB.
129
public static float[] RGBtoXYZ(float[] in)
131
float[] temp = new float[3];
132
float[] out = new float[3];
133
for (int i = 0; i < 3; i++)
134
if (in[i] <= 0.03928f)
135
temp[i] = in[i] / 12.92f;
137
temp[i] = (float) Math.exp(2.4 * Math.log((in[i] + 0.055) / 1.055));
140
* Note: The numbers which were used to calculate this only had four
141
* digits of accuracy. So don't be fooled by the number of digits here.
142
* If someone has more accurate source, feel free to update this.
144
out[0] = (float) (0.436063750222 * temp[0] + 0.385149601465 * temp[1]
145
+ 0.143086418888 * temp[2]);
146
out[1] = (float) (0.222450894035 * temp[0] + 0.71692584775 * temp[1]
147
+ 0.060624511256 * temp[2]);
148
out[2] = (float) (0.0138985186 * temp[0] + 0.097079690112 * temp[1]
149
+ 0.713996045725 * temp[2]);