Implement gamma correction for the LEDs

Instead of using the supplied linear color component values as-is,
convert them to gamma-corrected, non-linear values first. This way, we
can use numbers like 127 to mean half brightness, and have it
automatically translated to the correct, gamma-corrected value.

Table copied from:
 https://learn.adafruit.com/led-tricks-gamma-correction/the-quick-fix

This adds a bit over 256 bytes of code, but makes working with colors a
lot easier.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>

src/Kaleidoscope-Hardware-Model01.cpp

@@ -12,6 +12,25 @@ static constexpr uint8_t key_led_map[4][16] = {
   {0,7, 8,15,16,23,31,30,     33,32,40,47,48,55,56,63},
 };
 
+const uint8_t PROGMEM gamma8[] = {
+    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
+};
+
 Model01::Model01(void) {
 
 }
@@ -58,7 +77,13 @@ void Model01::setup(void) {
 }
 
 
-void Model01::led_set_crgb_at(uint8_t i, cRGB crgb) {
+void Model01::led_set_crgb_at(uint8_t i, cRGB crgb_) {
+    cRGB crgb;
+
+    crgb.r = pgm_read_byte(&gamma8[crgb_.r]);
+    crgb.g = pgm_read_byte(&gamma8[crgb_.g]);
+    crgb.b = pgm_read_byte(&gamma8[crgb_.b]);
+
     if(i<32) {
         cRGB oldColor = led_get_crgb_at(i);
         isLEDChanged |= !(oldColor.r == crgb.r && oldColor.g == crgb.g && oldColor.b == crgb.b);