1 /* 2 * Copyright 2018 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 androidx.core.animation; 18 19 import android.annotation.SuppressLint; 20 21 import org.jspecify.annotations.NonNull; 22 23 /** 24 * This evaluator can be used to perform type interpolation between integer 25 * values that represent ARGB colors. 26 */ 27 public final class ArgbEvaluator implements TypeEvaluator<Integer> { 28 private static final ArgbEvaluator sInstance = new ArgbEvaluator(); 29 30 /** 31 * Returns an instance of <code>ArgbEvaluator</code> that may be used in 32 * {@link ValueAnimator#setEvaluator(TypeEvaluator)}. The same instance may 33 * be used in multiple <code>Animator</code>s because it holds no state. 34 * @return An instance of <code>ArgbEvaluator</code>. 35 */ getInstance()36 public static @NonNull ArgbEvaluator getInstance() { 37 return sInstance; 38 } 39 ArgbEvaluator()40 private ArgbEvaluator() { 41 } 42 43 /** 44 * This function returns the calculated in-between value for a color 45 * given integers that represent the start and end values in the four 46 * bytes of the 32-bit int. Each channel is separately linearly interpolated 47 * and the resulting calculated values are recombined into the return value. 48 * 49 * @param fraction The fraction from the starting to the ending values 50 * @param startValue A 32-bit int value representing colors in the 51 * separate bytes of the parameter 52 * @param endValue A 32-bit int value representing colors in the 53 * separate bytes of the parameter 54 * @return A value that is calculated to be the linearly interpolated 55 * result, derived by separating the start and end values into separate 56 * color channels and interpolating each one separately, recombining the 57 * resulting values in the same way. 58 */ 59 @SuppressLint("AutoBoxing") /* Generics */ 60 @Override evaluate( float fraction, @SuppressLint("AutoBoxing") @NonNull Integer startValue, @SuppressLint("AutoBoxing") @NonNull Integer endValue )61 public @NonNull Integer evaluate( 62 float fraction, 63 @SuppressLint("AutoBoxing") @NonNull Integer startValue, 64 @SuppressLint("AutoBoxing") @NonNull Integer endValue 65 ) { 66 int startInt = startValue; 67 float startA = ((startInt >> 24) & 0xff) / 255.0f; 68 float startR = ((startInt >> 16) & 0xff) / 255.0f; 69 float startG = ((startInt >> 8) & 0xff) / 255.0f; 70 float startB = (startInt & 0xff) / 255.0f; 71 72 int endInt = endValue; 73 float endA = ((endInt >> 24) & 0xff) / 255.0f; 74 float endR = ((endInt >> 16) & 0xff) / 255.0f; 75 float endG = ((endInt >> 8) & 0xff) / 255.0f; 76 float endB = (endInt & 0xff) / 255.0f; 77 78 // convert from sRGB to linear 79 startR = (float) Math.pow(startR, 2.2); 80 startG = (float) Math.pow(startG, 2.2); 81 startB = (float) Math.pow(startB, 2.2); 82 83 endR = (float) Math.pow(endR, 2.2); 84 endG = (float) Math.pow(endG, 2.2); 85 endB = (float) Math.pow(endB, 2.2); 86 87 // compute the interpolated color in linear space 88 float a = startA + fraction * (endA - startA); 89 float r = startR + fraction * (endR - startR); 90 float g = startG + fraction * (endG - startG); 91 float b = startB + fraction * (endB - startB); 92 93 // convert back to sRGB in the [0..255] range 94 a = a * 255.0f; 95 r = (float) Math.pow(r, 1.0 / 2.2) * 255.0f; 96 g = (float) Math.pow(g, 1.0 / 2.2) * 255.0f; 97 b = (float) Math.pow(b, 1.0 / 2.2) * 255.0f; 98 99 return Math.round(a) << 24 | Math.round(r) << 16 | Math.round(g) << 8 | Math.round(b); 100 } 101 } 102