| /* |
| * Copyright (C) 2010 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package android.animation; |
| |
| /** |
| * This evaluator can be used to perform type interpolation between integer |
| * values that represent ARGB colors. |
| */ |
| public class ArgbEvaluator implements TypeEvaluator { |
| private static final ArgbEvaluator sInstance = new ArgbEvaluator(); |
| |
| /** |
| * Returns an instance of <code>ArgbEvaluator</code> that may be used in |
| * {@link ValueAnimator#setEvaluator(TypeEvaluator)}. The same instance may |
| * be used in multiple <code>Animator</code>s because it holds no state. |
| * @return An instance of <code>ArgbEvalutor</code>. |
| * |
| * @hide |
| */ |
| public static ArgbEvaluator getInstance() { |
| return sInstance; |
| } |
| |
| /** |
| * This function returns the calculated in-between value for a color |
| * given integers that represent the start and end values in the four |
| * bytes of the 32-bit int. Each channel is separately linearly interpolated |
| * and the resulting calculated values are recombined into the return value. |
| * |
| * @param fraction The fraction from the starting to the ending values |
| * @param startValue A 32-bit int value representing colors in the |
| * separate bytes of the parameter |
| * @param endValue A 32-bit int value representing colors in the |
| * separate bytes of the parameter |
| * @return A value that is calculated to be the linearly interpolated |
| * result, derived by separating the start and end values into separate |
| * color channels and interpolating each one separately, recombining the |
| * resulting values in the same way. |
| */ |
| public Object evaluate(float fraction, Object startValue, Object endValue) { |
| int startInt = (Integer) startValue; |
| float startA = ((startInt >> 24) & 0xff) / 255.0f; |
| float startR = ((startInt >> 16) & 0xff) / 255.0f; |
| float startG = ((startInt >> 8) & 0xff) / 255.0f; |
| float startB = ( startInt & 0xff) / 255.0f; |
| |
| int endInt = (Integer) endValue; |
| float endA = ((endInt >> 24) & 0xff) / 255.0f; |
| float endR = ((endInt >> 16) & 0xff) / 255.0f; |
| float endG = ((endInt >> 8) & 0xff) / 255.0f; |
| float endB = ( endInt & 0xff) / 255.0f; |
| |
| // convert from sRGB to linear |
| startR = (float) Math.pow(startR, 2.2); |
| startG = (float) Math.pow(startG, 2.2); |
| startB = (float) Math.pow(startB, 2.2); |
| |
| endR = (float) Math.pow(endR, 2.2); |
| endG = (float) Math.pow(endG, 2.2); |
| endB = (float) Math.pow(endB, 2.2); |
| |
| // compute the interpolated color in linear space |
| float a = startA + fraction * (endA - startA); |
| float r = startR + fraction * (endR - startR); |
| float g = startG + fraction * (endG - startG); |
| float b = startB + fraction * (endB - startB); |
| |
| // convert back to sRGB in the [0..255] range |
| a = a * 255.0f; |
| r = (float) Math.pow(r, 1.0 / 2.2) * 255.0f; |
| g = (float) Math.pow(g, 1.0 / 2.2) * 255.0f; |
| b = (float) Math.pow(b, 1.0 / 2.2) * 255.0f; |
| |
| return Math.round(a) << 24 | Math.round(r) << 16 | Math.round(g) << 8 | Math.round(b); |
| } |
| } |