| /* ToneReproductionCurve.java -- Representation of an ICC 'curv' type TRC |
| 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; |
| |
| |
| /** |
| * ToneReproductionCurve - TRCs are used to describe RGB |
| * and Grayscale profiles. The TRC is essentially the gamma |
| * function of the color space. |
| * |
| * For example, Apple RGB has a gamma of 1.8, most monitors are ~2.2, |
| * sRGB is 2.4 with a small linear part near 0. |
| * Linear spaces are of course 1.0. |
| * (The exact function is implemented in SrgbConverter) |
| * |
| * The ICC specification allows the TRC to be described as a single |
| * Gamma value, where the function is thus out = in**gamma. |
| * Alternatively, the gamma function may be represented by a lookup table |
| * of values, in which case linear interpolation is used. |
| * |
| * @author Sven de Marothy |
| */ |
| public class ToneReproductionCurve |
| { |
| private float[] trc; |
| private float gamma; |
| private float[] reverseTrc; |
| |
| /** |
| * Constructs a TRC from a gamma values |
| */ |
| public ToneReproductionCurve(float gamma) |
| { |
| trc = null; |
| reverseTrc = null; |
| this.gamma = gamma; |
| } |
| |
| /** |
| * Constructs a TRC from a set of float values |
| */ |
| public ToneReproductionCurve(float[] trcValues) |
| { |
| trc = new float[trcValues.length]; |
| System.arraycopy(trcValues, 0, trc, 0, trcValues.length); |
| setupReverseTrc(); |
| } |
| |
| /** |
| * Constructs a TRC from a set of short values normalized to |
| * the 0-65535 range (as in the ICC profile file). |
| * (Note the values are treated as unsigned) |
| */ |
| public ToneReproductionCurve(short[] trcValues) |
| { |
| trc = new float[trcValues.length]; |
| for (int i = 0; i < trcValues.length; i++) |
| trc[i] = (float) ((int) trcValues[i] & (0xFFFF)) / 65535.0f; |
| setupReverseTrc(); |
| } |
| |
| /** |
| * Performs a TRC lookup |
| */ |
| public float lookup(float in) |
| { |
| float out; |
| |
| if (trc == null) |
| { |
| if (in == 0f) |
| return 0.0f; |
| return (float) Math.exp(gamma * Math.log(in)); |
| } |
| else |
| { |
| double alpha = in * (trc.length - 1); |
| int index = (int) Math.floor(alpha); |
| alpha = alpha - (double) index; |
| if (index >= trc.length - 1) |
| return trc[trc.length - 1]; |
| if (index <= 0) |
| return trc[0]; |
| out = (float) (trc[index] * (1.0 - alpha) + trc[index + 1] * alpha); |
| } |
| return out; |
| } |
| |
| /** |
| * Performs an reverse lookup |
| */ |
| public float reverseLookup(float in) |
| { |
| float out; |
| |
| if (trc == null) |
| { |
| if (in == 0f) |
| return 0.0f; |
| return (float) Math.exp((1.0 / gamma) * Math.log(in)); |
| } |
| else |
| { |
| double alpha = in * (reverseTrc.length - 1); |
| int index = (int) Math.floor(alpha); |
| alpha = alpha - (double) index; |
| if (index >= reverseTrc.length - 1) |
| return reverseTrc[reverseTrc.length - 1]; |
| if (index <= 0) |
| return reverseTrc[0]; |
| out = (float) (reverseTrc[index] * (1.0 - alpha) |
| + reverseTrc[index + 1] * alpha); |
| } |
| return out; |
| } |
| |
| /** |
| * Calculates a reverse-lookup table. |
| * We use a whopping 10,000 entries.. This is should be more than any |
| * real-life TRC table (typically around 256-1024) so we won't be losing |
| * any precision. |
| * |
| * This will of course generate completely invalid results if the curve |
| * is not monotonic and invertable. But what's the alternative? |
| */ |
| public void setupReverseTrc() |
| { |
| reverseTrc = new float[10000]; |
| int j = 0; |
| for (int i = 0; i < 10000; i++) |
| { |
| float n = ((float) i) / 10000f; |
| while (trc[j + 1] < n && j < trc.length - 2) |
| j++; |
| |
| if (j == trc.length - 2) |
| reverseTrc[i] = trc[trc.length - 1]; |
| else |
| reverseTrc[i] = (j + (n - trc[j]) / (trc[j + 1] - trc[j])) / ((float) trc.length); |
| } |
| } |
| } |