Julius D'souza | 428aed0 | 2016-08-07 19:08:30 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2016 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 | |
| 17 | package com.android.server.display; |
| 18 | |
| 19 | import android.util.Slog; |
| 20 | |
| 21 | /** |
| 22 | * A helper class for handling access to illuminance hysteresis level values. |
| 23 | */ |
| 24 | final class HysteresisLevels { |
| 25 | private static final String TAG = "HysteresisLevels"; |
| 26 | |
| 27 | // Default hysteresis constraints for brightening or darkening. |
| 28 | // The recent lux must have changed by at least this fraction relative to the |
| 29 | // current ambient lux before a change will be considered. |
| 30 | private static final float DEFAULT_BRIGHTENING_HYSTERESIS = 0.10f; |
| 31 | private static final float DEFAULT_DARKENING_HYSTERESIS = 0.20f; |
| 32 | |
| 33 | private static final boolean DEBUG = false; |
| 34 | |
| 35 | private final float[] mBrightLevels; |
| 36 | private final float[] mDarkLevels; |
| 37 | private final float[] mLuxLevels; |
| 38 | |
| 39 | /** |
| 40 | * Creates a {@code HysteresisLevels} object with the given equal-length |
| 41 | * integer arrays. |
| 42 | * @param brightLevels an array of brightening hysteresis constraint constants |
| 43 | * @param darkLevels an array of darkening hysteresis constraint constants |
| 44 | * @param luxLevels a monotonically increasing array of illuminance |
| 45 | * thresholds in units of lux |
| 46 | */ |
| 47 | public HysteresisLevels(int[] brightLevels, int[] darkLevels, int[] luxLevels) { |
| 48 | if (brightLevels.length != darkLevels.length || darkLevels.length != luxLevels.length + 1) { |
| 49 | throw new IllegalArgumentException("Mismatch between hysteresis array lengths."); |
| 50 | } |
| 51 | mBrightLevels = setArrayFormat(brightLevels, 1000.0f); |
| 52 | mDarkLevels = setArrayFormat(darkLevels, 1000.0f); |
| 53 | mLuxLevels = setArrayFormat(luxLevels, 1.0f); |
| 54 | } |
| 55 | |
| 56 | /** |
| 57 | * Return the brightening hysteresis threshold for the given lux level. |
| 58 | */ |
| 59 | public float getBrighteningThreshold(float lux) { |
| 60 | float brightConstant = getReferenceLevel(lux, mBrightLevels); |
| 61 | float brightThreshold = lux * (1.0f + brightConstant); |
| 62 | if (DEBUG) { |
| 63 | Slog.d(TAG, "bright hysteresis constant=: " + brightConstant + ", threshold=" |
| 64 | + brightThreshold + ", lux=" + lux); |
| 65 | } |
| 66 | return brightThreshold; |
| 67 | } |
| 68 | |
| 69 | /** |
| 70 | * Return the darkening hysteresis threshold for the given lux level. |
| 71 | */ |
| 72 | public float getDarkeningThreshold(float lux) { |
| 73 | float darkConstant = getReferenceLevel(lux, mDarkLevels); |
| 74 | float darkThreshold = lux * (1.0f - darkConstant); |
| 75 | if (DEBUG) { |
| 76 | Slog.d(TAG, "dark hysteresis constant=: " + darkConstant + ", threshold=" |
| 77 | + darkThreshold + ", lux=" + lux); |
| 78 | } |
| 79 | return darkThreshold; |
| 80 | } |
| 81 | |
| 82 | /** |
| 83 | * Return the hysteresis constant for the closest lux threshold value to the |
| 84 | * current illuminance from the given array. |
| 85 | */ |
| 86 | private float getReferenceLevel(float lux, float[] referenceLevels) { |
| 87 | int index = 0; |
| 88 | while (mLuxLevels.length > index && lux >= mLuxLevels[index]) { |
| 89 | ++index; |
| 90 | } |
| 91 | return referenceLevels[index]; |
| 92 | } |
| 93 | |
| 94 | /** |
| 95 | * Return a float array where each i-th element equals {@code configArray[i]/divideFactor}. |
| 96 | */ |
| 97 | private float[] setArrayFormat(int[] configArray, float divideFactor) { |
| 98 | float[] levelArray = new float[configArray.length]; |
| 99 | for (int index = 0; levelArray.length > index; ++index) { |
| 100 | levelArray[index] = (float)configArray[index] / divideFactor; |
| 101 | } |
| 102 | return levelArray; |
| 103 | } |
| 104 | } |