OLD | NEW |
(Empty) | |
| 1 // Copyright 2016 The Chromium Authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. |
| 4 |
| 5 #include "device/base/device_util_mac.h" |
| 6 |
| 7 #include <math.h> |
| 8 |
| 9 namespace device { |
| 10 |
| 11 double LMUvalueToLux(uint64_t raw_value) { |
| 12 // Conversion formula from regression. |
| 13 // https://bugzilla.mozilla.org/show_bug.cgi?id=793728 |
| 14 // Let x = raw_value, then |
| 15 // lux = -2.978303814*(10^-27)*x^4 + 2.635687683*(10^-19)*x^3 - |
| 16 // 3.459747434*(10^-12)*x^2 + 3.905829689*(10^-5)*x - 0.1932594532 |
| 17 |
| 18 static const long double k4 = pow(10.L, -7); |
| 19 static const long double k3 = pow(10.L, -4); |
| 20 static const long double k2 = pow(10.L, -2); |
| 21 static const long double k1 = pow(10.L, 5); |
| 22 long double scaled_value = raw_value / k1; |
| 23 |
| 24 long double lux_value = |
| 25 (-3 * k4 * pow(scaled_value, 4)) + (2.6 * k3 * pow(scaled_value, 3)) + |
| 26 (-3.4 * k2 * pow(scaled_value, 2)) + (3.9 * scaled_value) - 0.19; |
| 27 |
| 28 double lux = ceil(static_cast<double>(lux_value)); |
| 29 return lux > 0 ? lux : 0; |
| 30 } |
| 31 |
| 32 } // namespace device |
OLD | NEW |