Merge pull request wled#4111 from DedeHai/0_15_PWM_CIEbrightnesscalc

replaced PWM LUT with calculation

Author: blazoncek

wled00/bus_manager.cpp

@@ -497,46 +497,19 @@ uint32_t BusPwm::getPixelColor(uint16_t pix) {
   return RGBW32(_data[0], _data[0], _data[0], _data[0]);
 }
 
-#ifndef ESP8266
-static const uint16_t cieLUT[256] = {
-	0, 2, 4, 5, 7, 9, 11, 13, 15, 16, 
-	18, 20, 22, 24, 26, 27, 29, 31, 33, 35, 
-	34, 36, 37, 39, 41, 43, 45, 47, 49, 52, 
-	54, 56, 59, 61, 64, 67, 69, 72, 75, 78, 
-	81, 84, 87, 90, 94, 97, 100, 104, 108, 111, 
-	115, 119, 123, 127, 131, 136, 140, 144, 149, 154, 
-	158, 163, 168, 173, 178, 183, 189, 194, 200, 205, 
-	211, 217, 223, 229, 235, 241, 247, 254, 261, 267, 
-	274, 281, 288, 295, 302, 310, 317, 325, 333, 341, 
-	349, 357, 365, 373, 382, 391, 399, 408, 417, 426, 
-	436, 445, 455, 464, 474, 484, 494, 505, 515, 526, 
-	536, 547, 558, 569, 580, 592, 603, 615, 627, 639, 
-	651, 663, 676, 689, 701, 714, 727, 741, 754, 768, 
-	781, 795, 809, 824, 838, 853, 867, 882, 897, 913, 
-	928, 943, 959, 975, 991, 1008, 1024, 1041, 1058, 1075, 
-	1092, 1109, 1127, 1144, 1162, 1180, 1199, 1217, 1236, 1255, 
-	1274, 1293, 1312, 1332, 1352, 1372, 1392, 1412, 1433, 1454, 
-	1475, 1496, 1517, 1539, 1561, 1583, 1605, 1628, 1650, 1673, 
-	1696, 1719, 1743, 1767, 1791, 1815, 1839, 1864, 1888, 1913, 
-	1939, 1964, 1990, 2016, 2042, 2068, 2095, 2121, 2148, 2176, 
-	2203, 2231, 2259, 2287, 2315, 2344, 2373, 2402, 2431, 2461, 
-	2491, 2521, 2551, 2581, 2612, 2643, 2675, 2706, 2738, 2770, 
-	2802, 2835, 2867, 2900, 2934, 2967, 3001, 3035, 3069, 3104, 
-	3138, 3174, 3209, 3244, 3280, 3316, 3353, 3389, 3426, 3463, 
-	3501, 3539, 3576, 3615, 3653, 3692, 3731, 3770, 3810, 3850, 
-	3890, 3930, 3971, 4012, 4053, 4095
-};
-#endif
-
 void BusPwm::show() {
   if (!_valid) return;
   unsigned numPins = NUM_PWM_PINS(_type);
   unsigned maxBri = (1<<_depth) - 1;
-  #ifdef ESP8266
-  unsigned pwmBri = (unsigned)(roundf(powf((float)_bri / 255.0f, 1.7f) * (float)maxBri)); // using gamma 1.7 to extrapolate PWM duty cycle
-  #else
-  unsigned pwmBri = cieLUT[_bri] >> (12 - _depth); // use CIE LUT
-  #endif
+  // use CIE brightness formula
+  unsigned pwmBri = (unsigned)_bri * 100;  
+  if(pwmBri < 2040) pwmBri = ((pwmBri << _depth) + 115043) / 230087; //adding '0.5' before division for correct rounding
+  else {  
+    pwmBri += 4080;
+    float temp = (float)pwmBri / 29580;
+    temp = temp * temp * temp * (1<<_depth) - 1; 
+    pwmBri = (unsigned)temp;
+  }
   for (unsigned i = 0; i < numPins; i++) {
     unsigned scaled = (_data[i] * pwmBri) / 255;
     if (_reversed) scaled = maxBri - scaled;