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      1 /*
      2  * Copyright (C) 2013 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 com.android.camera.util;
     18 
     19 import android.animation.TimeInterpolator;
     20 
     21 /**
     22  * Interpolator that uses a Bezier derived S shaped curve.
     23  *
     24  * TODO: Replace usages with ui.motion classes.
     25  */
     26 public class Gusterpolator implements TimeInterpolator {
     27     /** An instance of {@link Gusterpolator}. */
     28     public static final Gusterpolator INSTANCE = new Gusterpolator();
     29 
     30     /**
     31      * To avoid users of this class creating multiple copies needlessly, the constructor is
     32      * private.
     33      */
     34     private Gusterpolator() {}
     35 
     36     /**
     37      * Lookup table values.
     38      * Generated using a Bezier curve from (0,0) to (1,1) with control points:
     39      * P0 (0,0)
     40      * P1 (0.4, 0)
     41      * P2 (0.2, 1.0)
     42      * P3 (1.0, 1.0)
     43      *
     44      * Values sampled with x at regular intervals between 0 and 1.
     45      */
     46     private static final float[] VALUES = new float[] {
     47             0.0f, 0.0002f, 0.0009f, 0.0019f, 0.0036f, 0.0059f, 0.0086f, 0.0119f, 0.0157f, 0.0209f,
     48             0.0257f, 0.0321f, 0.0392f, 0.0469f, 0.0566f, 0.0656f, 0.0768f, 0.0887f, 0.1033f,
     49             0.1186f, 0.1349f, 0.1519f, 0.1696f, 0.1928f, 0.2121f, 0.237f, 0.2627f, 0.2892f, 0.3109f,
     50             0.3386f, 0.3667f, 0.3952f, 0.4241f, 0.4474f, 0.4766f, 0.5f, 0.5234f, 0.5468f, 0.5701f,
     51             0.5933f, 0.6134f, 0.6333f, 0.6531f, 0.6698f, 0.6891f, 0.7054f, 0.7214f, 0.7346f,
     52             0.7502f, 0.763f, 0.7756f, 0.7879f, 0.8f, 0.8107f, 0.8212f, 0.8326f, 0.8415f, 0.8503f,
     53             0.8588f, 0.8672f, 0.8754f, 0.8833f, 0.8911f, 0.8977f, 0.9041f, 0.9113f, 0.9165f,
     54             0.9232f, 0.9281f, 0.9328f, 0.9382f, 0.9434f, 0.9476f, 0.9518f, 0.9557f, 0.9596f,
     55             0.9632f, 0.9662f, 0.9695f, 0.9722f, 0.9753f, 0.9777f, 0.9805f, 0.9826f, 0.9847f,
     56             0.9866f, 0.9884f, 0.9901f, 0.9917f, 0.9931f, 0.9944f, 0.9955f, 0.9964f, 0.9973f,
     57             0.9981f, 0.9986f, 0.9992f, 0.9995f, 0.9998f, 1.0f, 1.0f
     58     };
     59 
     60     private static final float STEP_SIZE = 1.0f / (VALUES.length - 1);
     61 
     62     @Override
     63     public float getInterpolation(float input) {
     64         if (input >= 1.0f) {
     65             return 1.0f;
     66         }
     67 
     68         if (input <= 0f) {
     69             return 0f;
     70         }
     71 
     72         int position = Math.min(
     73                 (int)(input * (VALUES.length - 1)),
     74                 VALUES.length - 2);
     75 
     76         float quantized = position * STEP_SIZE;
     77         float difference = input - quantized;
     78         float weight = difference / STEP_SIZE;
     79 
     80         return VALUES[position] + weight * (VALUES[position + 1] - VALUES[position]);
     81     }
     82 }
     83