1/*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5 * in compliance with the License. You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the License
10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11 * or implied. See the License for the specific language governing permissions and limitations under
12 * the License.
13 */
14package android.support.v17.leanback.animation;
15
16import android.animation.TimeInterpolator;
17
18/**
19 * @hide
20 */
21public class LogAccelerateInterpolator implements TimeInterpolator {
22
23    int mBase;
24    int mDrift;
25    final float mLogScale;
26
27    public LogAccelerateInterpolator(int base, int drift) {
28        mBase = base;
29        mDrift = drift;
30        mLogScale = 1f / computeLog(1, mBase, mDrift);
31    }
32
33    static float computeLog(float t, int base, int drift) {
34        return (float) -Math.pow(base, -t) + 1 + (drift * t);
35    }
36
37    @Override
38    public float getInterpolation(float t) {
39        return 1 - computeLog(1 - t, mBase, mDrift) * mLogScale;
40    }
41}
42