Add gamma correction to vor_rgbled.

Author: kenkus-futurice

vor-arduino/vor_rgbled.cpp

@@ -25,15 +25,15 @@ VorRgbLed::~VorRgbLed() {
 }
 
 void VorRgbLed::writeRed(int value) {
-    _red->write(MAX_ANALOG_OUTPUT_VALUE - value);
+    _red->write(pgm_read_byte(&GAMMA[MAX_ANALOG_OUTPUT_VALUE - value]));
 }
 
 void VorRgbLed::writeGreen(int value) {
-    _green->write(MAX_ANALOG_OUTPUT_VALUE - value);
+    _green->write(pgm_read_byte(&GAMMA[MAX_ANALOG_OUTPUT_VALUE - value]));
 }
 
 void VorRgbLed::writeBlue(int value) {
-    _blue->write(MAX_ANALOG_OUTPUT_VALUE - value);
+    _blue->write(pgm_read_byte(&GAMMA[MAX_ANALOG_OUTPUT_VALUE - value]));
 }
 
 void VorRgbLed::write(int red, int green, int blue) {

vor-arduino/vor_rgbled.h

@@ -9,6 +9,26 @@
 #include "vor_actuator.h"
 #include "env.h"
 
+// Gamma correction lookup table
+// https://learn.adafruit.com/led-tricks-gamma-correction/the-quick-fix
+const uint8_t PROGMEM GAMMA[] = {
+    0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
+    0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  1,  1,  1,  1,
+    1,  1,  1,  1,  1,  1,  1,  1,  1,  2,  2,  2,  2,  2,  2,  2,
+    2,  3,  3,  3,  3,  3,  3,  3,  4,  4,  4,  4,  4,  5,  5,  5,
+    5,  6,  6,  6,  6,  7,  7,  7,  7,  8,  8,  8,  9,  9,  9, 10,
+   10, 10, 11, 11, 11, 12, 12, 13, 13, 13, 14, 14, 15, 15, 16, 16,
+   17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, 23, 24, 24, 25,
+   25, 26, 27, 27, 28, 29, 29, 30, 31, 32, 32, 33, 34, 35, 35, 36,
+   37, 38, 39, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 50,
+   51, 52, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 66, 67, 68,
+   69, 70, 72, 73, 74, 75, 77, 78, 79, 81, 82, 83, 85, 86, 87, 89,
+   90, 92, 93, 95, 96, 98, 99,101,102,104,105,107,109,110,112,114,
+  115,117,119,120,122,124,126,127,129,131,133,135,137,138,140,142,
+  144,146,148,150,152,154,156,158,160,162,164,167,169,171,173,175,
+  177,180,182,184,186,189,191,193,196,198,200,203,205,208,210,213,
+  215,218,220,223,225,228,231,233,236,239,241,244,247,249,252,255 };
+
 class VorRgbLed{
 public:
     VorRgbLed(int redPin, int greenPin, int bluePin);
@@ -23,6 +43,7 @@ class VorRgbLed{
     VorActuator* _red;
     VorActuator* _green;
     VorActuator* _blue;
+
 };
 
 #endif