| /* 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., 59 Temple Place, Suite 330, Boston, MA |
| 02111-1307 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; |
| } |
| } |