sdk/sources/android-23/android/support/v17/leanback/animation/LogAccelerateInterpolator.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 android.support.v17.leanback.animation;

import android.animation.TimeInterpolator;

/**
 * @hide
 */
public class LogAccelerateInterpolator implements TimeInterpolator {

    int mBase;
    int mDrift;
    final float mLogScale;

    public LogAccelerateInterpolator(int base, int drift) {
        mBase = base;
        mDrift = drift;
        mLogScale = 1f / computeLog(1, mBase, mDrift);
    }

    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 1 - computeLog(1 - t, mBase, mDrift) * mLogScale;
    }
}