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+/* SrgbConverter.java -- sRGB conversion class
+ Copyright (C) 2004 Free Software Foundation
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU Classpath is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING. If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library. Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module. An independent module is a module which is not derived from
+or based on this library. If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so. If you do not wish to do so, delete this
+exception statement from your version. */
+
+package gnu.java.awt.color;
+
+
+/**
+ * SrgbConverter - conversion routines for the sRGB colorspace
+ * sRGB is a standard for RGB colorspaces, adopted by the w3c.
+ *
+ * The specification is available at:
+ * http://www.w3.org/Graphics/Color/sRGB.html
+ *
+ * @author Sven de Marothy
+ */
+/**
+ *
+ * Note the matrix numbers used here are NOT identical to those in the
+ * w3 spec, as those numbers are CIE XYZ relative a D65 white point.
+ * The CIE XYZ we use is relative a D50 white point, so therefore a
+ * linear Bradford transform matrix for D65->D50 mapping has been applied.
+ * (The ICC documents describe this transform)
+ *
+ * Linearized Bradford transform:
+ * 0.8951 0.2664 -0.1614
+ * -0.7502 1.7135 0.0367
+ * 0.0389 -0.0685 1.0296
+ *
+ * Inverse:
+ * 0.9870 -0.1471 0.1600
+ * 0.4323 0.5184 0.0493
+ * -0.00853 0.0400 0.9685
+ */
+public class SrgbConverter implements ColorSpaceConverter
+{
+ public float[] fromCIEXYZ(float[] in)
+ {
+ return XYZtoRGB(in);
+ }
+
+ public float[] toCIEXYZ(float[] in)
+ {
+ return RGBtoXYZ(in);
+ }
+
+ public float[] toRGB(float[] in)
+ {
+ float[] out = new float[3];
+ System.arraycopy(in, 0, out, 0, 3);
+ return out;
+ }
+
+ public float[] fromRGB(float[] in)
+ {
+ float[] out = new float[3];
+ System.arraycopy(in, 0, out, 0, 3);
+ return out;
+ }
+
+ /**
+ * CIE XYZ (D50 relative) --> sRGB
+ *
+ * Static as it's used by other ColorSpaceConverters to
+ * convert to sRGB if the color space is defined in XYZ.
+ */
+ public static float[] XYZtoRGB(float[] in)
+ {
+ float[] temp = new float[3];
+ temp[0] = 3.1338f * in[0] - 1.6171f * in[1] - 0.4907f * in[2];
+ temp[1] = -0.9785f * in[0] + 1.9160f * in[1] + 0.0334f * in[2];
+ temp[2] = 0.0720f * in[0] - 0.2290f * in[1] + 1.4056f * in[2];
+
+ float[] out = new float[3];
+ for (int i = 0; i < 3; i++)
+ {
+ if (temp[i] < 0)
+ temp[i] = 0.0f;
+ if (temp[i] > 1)
+ temp[i] = 1.0f;
+ if (temp[i] <= 0.00304f)
+ out[i] = temp[i] * 12.92f;
+ else
+ out[i] = 1.055f * ((float) Math.exp((1 / 2.4) * Math.log(temp[i])))
+ - 0.055f;
+ }
+ return out;
+ }
+
+ /**
+ * sRGB --> CIE XYZ (D50 relative)
+ *
+ * Static as it's used by other ColorSpaceConverters to
+ * convert to XYZ if the color space is defined in RGB.
+ */
+ public static float[] RGBtoXYZ(float[] in)
+ {
+ float[] temp = new float[3];
+ float[] out = new float[3];
+ for (int i = 0; i < 3; i++)
+ if (in[i] <= 0.03928f)
+ temp[i] = in[i] / 12.92f;
+ else
+ temp[i] = (float) Math.exp(2.4 * Math.log((in[i] + 0.055) / 1.055));
+
+ /*
+ * Note: The numbers which were used to calculate this only had four
+ * digits of accuracy. So don't be fooled by the number of digits here.
+ * If someone has more accurate source, feel free to update this.
+ */
+ out[0] = (float) (0.436063750222 * temp[0] + 0.385149601465 * temp[1]
+ + 0.143086418888 * temp[2]);
+ out[1] = (float) (0.222450894035 * temp[0] + 0.71692584775 * temp[1]
+ + 0.060624511256 * temp[2]);
+ out[2] = (float) (0.0138985186 * temp[0] + 0.097079690112 * temp[1]
+ + 0.713996045725 * temp[2]);
+ return out;
+ }
+}