1 /* 2 * Copyright (C) 2010 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package android.animation; 18 19 import android.compat.annotation.UnsupportedAppUsage; 20 21 /** 22 * This evaluator can be used to perform type interpolation between integer 23 * values that represent ARGB colors. 24 */ 25 public class ArgbEvaluator implements TypeEvaluator { 26 private static final ArgbEvaluator sInstance = new ArgbEvaluator(); 27 28 /** 29 * Returns an instance of <code>ArgbEvaluator</code> that may be used in 30 * {@link ValueAnimator#setEvaluator(TypeEvaluator)}. The same instance may 31 * be used in multiple <code>Animator</code>s because it holds no state. 32 * @return An instance of <code>ArgbEvalutor</code>. 33 * 34 * @hide 35 */ 36 @UnsupportedAppUsage getInstance()37 public static ArgbEvaluator getInstance() { 38 return sInstance; 39 } 40 41 /** 42 * This function returns the calculated in-between value for a color 43 * given integers that represent the start and end values in the four 44 * bytes of the 32-bit int. Each channel is separately linearly interpolated 45 * and the resulting calculated values are recombined into the return value. 46 * 47 * @param fraction The fraction from the starting to the ending values 48 * @param startValue A 32-bit int value representing colors in the 49 * separate bytes of the parameter 50 * @param endValue A 32-bit int value representing colors in the 51 * separate bytes of the parameter 52 * @return A value that is calculated to be the linearly interpolated 53 * result, derived by separating the start and end values into separate 54 * color channels and interpolating each one separately, recombining the 55 * resulting values in the same way. 56 */ evaluate(float fraction, Object startValue, Object endValue)57 public Object evaluate(float fraction, Object startValue, Object endValue) { 58 int startInt = (Integer) startValue; 59 float startA = ((startInt >> 24) & 0xff) / 255.0f; 60 float startR = ((startInt >> 16) & 0xff) / 255.0f; 61 float startG = ((startInt >> 8) & 0xff) / 255.0f; 62 float startB = ( startInt & 0xff) / 255.0f; 63 64 int endInt = (Integer) endValue; 65 float endA = ((endInt >> 24) & 0xff) / 255.0f; 66 float endR = ((endInt >> 16) & 0xff) / 255.0f; 67 float endG = ((endInt >> 8) & 0xff) / 255.0f; 68 float endB = ( endInt & 0xff) / 255.0f; 69 70 // convert from sRGB to linear 71 startR = (float) Math.pow(startR, 2.2); 72 startG = (float) Math.pow(startG, 2.2); 73 startB = (float) Math.pow(startB, 2.2); 74 75 endR = (float) Math.pow(endR, 2.2); 76 endG = (float) Math.pow(endG, 2.2); 77 endB = (float) Math.pow(endB, 2.2); 78 79 // compute the interpolated color in linear space 80 float a = startA + fraction * (endA - startA); 81 float r = startR + fraction * (endR - startR); 82 float g = startG + fraction * (endG - startG); 83 float b = startB + fraction * (endB - startB); 84 85 // convert back to sRGB in the [0..255] range 86 a = a * 255.0f; 87 r = (float) Math.pow(r, 1.0 / 2.2) * 255.0f; 88 g = (float) Math.pow(g, 1.0 / 2.2) * 255.0f; 89 b = (float) Math.pow(b, 1.0 / 2.2) * 255.0f; 90 91 return Math.round(a) << 24 | Math.round(r) << 16 | Math.round(g) << 8 | Math.round(b); 92 } 93 }