| // Copyright 2016 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "device/sensors/public/cpp/device_util_mac.h" |
| |
| #include <math.h> |
| |
| namespace device { |
| |
| double LMUvalueToLux(uint64_t raw_value) { |
| // Conversion formula from regression. |
| // https://bugzilla.mozilla.org/show_bug.cgi?id=793728 |
| // Let x = raw_value, then |
| // lux = -2.978303814*(10^-27)*x^4 + 2.635687683*(10^-19)*x^3 - |
| // 3.459747434*(10^-12)*x^2 + 3.905829689*(10^-5)*x - 0.1932594532 |
| |
| static const long double k4 = pow(10.L, -7); |
| static const long double k3 = pow(10.L, -4); |
| static const long double k2 = pow(10.L, -2); |
| static const long double k1 = pow(10.L, 5); |
| long double scaled_value = raw_value / k1; |
| |
| long double lux_value = |
| (-3 * k4 * pow(scaled_value, 4)) + (2.6 * k3 * pow(scaled_value, 3)) + |
| (-3.4 * k2 * pow(scaled_value, 2)) + (3.9 * scaled_value) - 0.19; |
| |
| double lux = ceil(static_cast<double>(lux_value)); |
| return lux > 0 ? lux : 0; |
| } |
| |
| } // namespace device |
