1/*
2 * Copyright (C) 2007 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
17package com.android.dreams.phototable;
18
19import android.view.animation.DecelerateInterpolator;
20import android.view.animation.Interpolator;
21import android.view.animation.LinearInterpolator;
22
23/**
24 * An interpolator where the rate of change starts out quickly and
25 * and then decelerates.
26 *
27 */
28public class SoftLandingInterpolator implements Interpolator {
29    private final LinearInterpolator fly;
30    private final DecelerateInterpolator slide;
31    private final float mI;
32    private final float mO;
33    private final float upperRange;
34    private final float bottom;
35    private final float top;
36
37    public SoftLandingInterpolator(float i, float o) {
38        fly = new LinearInterpolator();
39        slide = new  DecelerateInterpolator();
40        mI = i;
41        mO = o;
42        final float epsilon = Math.min(mI / 2f, (1f - mI) / 2f);
43        bottom = mI - epsilon;
44        top = mI + epsilon;
45        upperRange = 1f - bottom;
46    }
47
48    public float getInterpolation(float input) {
49        final float f = fly.getInterpolation(input / upperRange) * mO;
50        final float s = slide.getInterpolation((input - bottom) / upperRange) * (1f - mO) + mO;
51
52        float value;
53        if (input < bottom) {
54            value = f;
55        } else if (input < top) {
56            final float alpha = (input - bottom) / (top - bottom);
57            value = (1f - alpha) * f + alpha * s;
58        } else {
59            value = s;
60        }
61
62        return value;
63    }
64}
65