| /* GrayScaleConverter.java -- Linear grayscale 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; |
| |
| |
| /** |
| * Linear Grayscale converter |
| * |
| * @author Sven de Marothy |
| */ |
| public class GrayScaleConverter implements ColorSpaceConverter |
| { |
| // intensity factors (ITU Rec. BT.709) |
| double[] coeff = { 0.2125f, 0.7154f, 0.0721f }; |
| |
| /** |
| * CIE 1931 D50 white point (in Lab coordinates) |
| */ |
| private static float[] D50 = { 0.96422f, 1.00f, 0.82521f }; |
| |
| public float[] toCIEXYZ(float[] in) |
| { |
| float g = in[0]; |
| if (g < 0) |
| g = 1 + g; |
| float[] out = { g * D50[0], g * D50[1], g * D50[2] }; // White spot |
| return out; |
| } |
| |
| public float[] toRGB(float[] in) |
| { |
| float[] out = new float[3]; |
| if (in[0] <= 0.00304f) |
| out[0] = in[0] * 12.92f; |
| else |
| out[0] = 1.055f * ((float) Math.exp((1 / 2.4) * Math.log(in[0]))) |
| - 0.055f; |
| out[1] = out[2] = out[0]; |
| return out; |
| } |
| |
| public float[] fromCIEXYZ(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[1]; |
| for (int i = 0; i < 3; i++) |
| out[0] = (float) (temp[i] * coeff[i]); |
| return out; |
| } |
| |
| public float[] fromRGB(float[] in) |
| { |
| float[] out = new float[1]; |
| |
| // Convert non-linear RGB coordinates to linear ones, |
| // numbers from the w3 spec. |
| out[0] = 0; |
| for (int i = 0; i < 3; i++) |
| { |
| float n = in[i]; |
| if (n < 0) |
| n = 0f; |
| if (n > 1) |
| n = 1f; |
| if (n <= 0.03928f) |
| out[0] += (float) (coeff[i] * n / 12.92); |
| else |
| out[0] += (float) (coeff[i] * Math.exp(2.4 * Math.log((n + 0.055) / 1.055))); |
| } |
| return out; |
| } |
| } |