interpolator/interpolator/src/main/java/androidx/interpolator/view/animation/FastOutExtraSlowInInterpolator.java

/*
 * Copyright 2022 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 androidx.interpolator.view.animation;

import android.view.animation.Interpolator;

/**
 * Interpolator corresponding to {@link android.R.interpolator#fast_out_extra_slow_in}.
 *
 * Uses a lookup table for a path consisting of two Bezier curves from (0,0) to (1,1).
 *
 * The first curve has control points:
 * P0 (0, 0)
 * P1 (0.05, 0)
 * P2 (0.133333, 0.06)
 * P3 (0.166666, 0.4)
 *
 * The second curve has control points:
 * P0 (0.166666, 0.4)
 * P1 (0.208333, 0.82)
 * P2 (0.25, 1)
 * P3 (1, 1)
 *
 * Values were generated with the following Kotlin code:
 * <code><pre>
 * val output = StringBuilder()
 * if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
 *     val p = Path()
 *     p.cubicTo(0.05f, 0f, 0.133333f, 0.06f, 0.166666f, 0.4f)
 *     p.cubicTo(0.208333f, 0.82f, 0.25f, 1.0f, 1.0f, 1.0f)
 *     val interpolator = PathInterpolator(p)
 *     val xDiff = 1.0f / 200
 *     for (i in 0..200) {
 *         val interpolatedValue = interpolator.getInterpolation(xDiff * i)
 *         output.append(String.format("%.4f", interpolatedValue))
 *         output.append("f, ")
 *     }
 *     println(output)
 * }
 * </pre></code>
 */
public class FastOutExtraSlowInInterpolator implements Interpolator {

    /**
     * Lookup table values sampled with x at regular intervals between 0 and 1 for a total of
     * 201 points.
     */
    private static final float[] VALUES = new float[] {
            0.0000f, 0.0008f, 0.0016f, 0.0024f, 0.0032f, 0.0057f, 0.0083f,
            0.0109f, 0.0134f, 0.0171f, 0.0218f, 0.0266f, 0.0313f, 0.0360f,
            0.0431f, 0.0506f, 0.0581f, 0.0656f, 0.0733f, 0.0835f, 0.0937f,
            0.1055f, 0.1179f, 0.1316f, 0.1466f, 0.1627f, 0.1810f, 0.2003f,
            0.2226f, 0.2468f, 0.2743f, 0.3060f, 0.3408f, 0.3852f, 0.4317f,
            0.4787f, 0.5177f, 0.5541f, 0.5834f, 0.6123f, 0.6333f, 0.6542f,
            0.6739f, 0.6887f, 0.7035f, 0.7183f, 0.7308f, 0.7412f, 0.7517f,
            0.7621f, 0.7725f, 0.7805f, 0.7879f, 0.7953f, 0.8027f, 0.8101f,
            0.8175f, 0.8230f, 0.8283f, 0.8336f, 0.8388f, 0.8441f, 0.8494f,
            0.8546f, 0.8592f, 0.8630f, 0.8667f, 0.8705f, 0.8743f, 0.8780f,
            0.8818f, 0.8856f, 0.8893f, 0.8927f, 0.8953f, 0.8980f, 0.9007f,
            0.9034f, 0.9061f, 0.9087f, 0.9114f, 0.9141f, 0.9168f, 0.9194f,
            0.9218f, 0.9236f, 0.9255f, 0.9274f, 0.9293f, 0.9312f, 0.9331f,
            0.9350f, 0.9368f, 0.9387f, 0.9406f, 0.9425f, 0.9444f, 0.9460f,
            0.9473f, 0.9486f, 0.9499f, 0.9512f, 0.9525f, 0.9538f, 0.9551f,
            0.9564f, 0.9577f, 0.9590f, 0.9603f, 0.9616f, 0.9629f, 0.9642f,
            0.9654f, 0.9663f, 0.9672f, 0.9680f, 0.9689f, 0.9697f, 0.9706f,
            0.9715f, 0.9723f, 0.9732f, 0.9741f, 0.9749f, 0.9758f, 0.9766f,
            0.9775f, 0.9784f, 0.9792f, 0.9801f, 0.9808f, 0.9813f, 0.9819f,
            0.9824f, 0.9829f, 0.9835f, 0.9840f, 0.9845f, 0.9850f, 0.9856f,
            0.9861f, 0.9866f, 0.9872f, 0.9877f, 0.9882f, 0.9887f, 0.9893f,
            0.9898f, 0.9903f, 0.9909f, 0.9914f, 0.9917f, 0.9920f, 0.9922f,
            0.9925f, 0.9928f, 0.9931f, 0.9933f, 0.9936f, 0.9939f, 0.9942f,
            0.9944f, 0.9947f, 0.9950f, 0.9953f, 0.9955f, 0.9958f, 0.9961f,
            0.9964f, 0.9966f, 0.9969f, 0.9972f, 0.9975f, 0.9977f, 0.9979f,
            0.9981f, 0.9982f, 0.9983f, 0.9984f, 0.9986f, 0.9987f, 0.9988f,
            0.9989f, 0.9991f, 0.9992f, 0.9993f, 0.9994f, 0.9995f, 0.9995f,
            0.9996f, 0.9996f, 0.9997f, 0.9997f, 0.9997f, 0.9998f, 0.9998f,
            0.9998f, 0.9999f, 0.9999f, 1.0000f, 1.0000f
    };
    private static final float STEP = 1f / (VALUES.length - 1);

    @Override
    public float getInterpolation(float input) {
        return LookupTableInterpolator.interpolate(VALUES, STEP, input);
    }
}