policy/src/com/android/internal/policy/impl/LogDecelerateInterpolator.java

/*
 * Copyright (C) 2014 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License
 */

package com.android.internal.policy.impl;

import android.view.animation.Interpolator;

public class LogDecelerateInterpolator implements Interpolator {

    private int mBase;
    private int mDrift;
    private final float mLogScale;

    public LogDecelerateInterpolator(int base, int drift) {
        mBase = base;
        mDrift = drift;

        mLogScale = 1f / computeLog(1, mBase, mDrift);
    }

    private static float computeLog(float t, int base, int drift) {
        return (float) -Math.pow(base, -t) + 1 + (drift * t);
    }

    @Override
    public float getInterpolation(float t) {
        return computeLog(t, mBase, mDrift) * mLogScale;
    }
}