68 lines
2.4 KiB
Java
68 lines
2.4 KiB
Java
/*
|
|
* Copyright (C) 2016 The CyanogenMod 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 org.cyanogenmod.internal.util;
|
|
|
|
public final class MathUtils {
|
|
|
|
/**
|
|
* Given a range of values which change continuously in a non-linear way,
|
|
* we can map back and forth to a linear scale using some quadratic equations.
|
|
*
|
|
* The linear scale ranges from 0 -> 1. This method will calculate the
|
|
* coefficients needed to solve the conversion functions in the next two methods.
|
|
*
|
|
* lower = actual value when linear value = 0
|
|
* mid = actual value when linear value = .5
|
|
* upper actual value when linear value = 1
|
|
*
|
|
* @param lower
|
|
* @param mid
|
|
* @param upper
|
|
* @return array of coefficients
|
|
*/
|
|
public static double[] powerCurve(double lower, double mid, double upper) {
|
|
final double[] curve = new double[3];
|
|
curve[0] = ((lower * upper) - (mid * mid)) / (lower - (2 * mid) + upper);
|
|
curve[1] = Math.pow((mid - lower), 2) / (lower - (2 * mid) + upper);
|
|
curve[2] = 2 * Math.log((upper - mid) / (mid - lower));
|
|
return curve;
|
|
}
|
|
|
|
/**
|
|
* Map a value on a power curve to a linear value
|
|
*
|
|
* @param curve obtained from powerCurve()
|
|
* @param value to convert to linear scale
|
|
* @return linear value from 0 -> 1
|
|
*/
|
|
public static double powerCurveToLinear(final double[] curve, double value) {
|
|
return Math.log((value - curve[0]) / curve[1]) / curve[2];
|
|
}
|
|
|
|
/**
|
|
* Map a value on a linear scale to a value on a power curve
|
|
*
|
|
* @param curve obtained from powerCurve()
|
|
* @param value from 0 -> 1 to map onto power curve
|
|
* @return actual value on the given curve
|
|
*/
|
|
public static double linearToPowerCurve(final double[] curve, double value) {
|
|
return curve[0] + curve[1] * Math.exp(curve[2] * value);
|
|
}
|
|
|
|
|
|
}
|