Added HSV2RGB and RGB2HSV functions for higher accuracy conversions

- also added a struct to handle HSV with 16bit hue better (including some conversions, can be extended easily)
- the functions are optimized for speed and flash use. They are faster and more accurate than what fastled offers (and use much less flash).
- replaced colorHStoRGB() with a call to the new hsv2rgb() function, saving even more flash (new function is untested!)
- the 16bit hue calculations result in an almost perfect conversion from RGB to HSV and back, the maximum error was 1/255 in the cases I tested.

wled00/colors.cpp

@@ -239,26 +239,64 @@ CRGBPalette16 generateRandomPalette()  //generate fully random palette
                        CHSV(random8(), random8(160, 255), random8(128, 255)));
 }
 
-void colorHStoRGB(uint16_t hue, byte sat, byte* rgb) //hue, sat to rgb
+void hsv2rgb(const CHSV32& hsv, uint32_t& rgb) // convert HSV (16bit hue) to RGB (32bit with white = 0)
 {
-  float h = ((float)hue)/10922.5f; // hue*6/65535
-  float s = ((float)sat)/255.0f;
-  int   i = int(h);
-  float f = h - i;
-  int   p = int(255.0f * (1.0f-s));
-  int   q = int(255.0f * (1.0f-s*f));
-  int   t = int(255.0f * (1.0f-s*(1.0f-f)));
-  p = constrain(p, 0, 255);
-  q = constrain(q, 0, 255);
-  t = constrain(t, 0, 255);
-  switch (i%6) {
-    case 0: rgb[0]=255,rgb[1]=t,  rgb[2]=p;  break;
-    case 1: rgb[0]=q,  rgb[1]=255,rgb[2]=p;  break;
-    case 2: rgb[0]=p,  rgb[1]=255,rgb[2]=t;  break;
-    case 3: rgb[0]=p,  rgb[1]=q,  rgb[2]=255;break;
-    case 4: rgb[0]=t,  rgb[1]=p,  rgb[2]=255;break;
-    case 5: rgb[0]=255,rgb[1]=p,  rgb[2]=q;  break;
+  unsigned int remainder, region, p, q, t;
+  unsigned int h = hsv.h;
+  unsigned int s = hsv.s;
+  unsigned int v = hsv.v;
+  if (s == 0) {
+      rgb = v << 16 | v << 8 | v;
+      return;
   }
+  region = h / 10923;  // 65536 / 6 = 10923
+  remainder = (h - (region * 10923)) * 6;
+  p = (v * (256 - s)) >> 8;
+  q = (v * (255 - ((s * remainder) >> 16))) >> 8;
+  t = (v * (255 - ((s * (65535 - remainder)) >> 16))) >> 8;
+  switch (region) {
+    case 0:
+      rgb = v << 16 | t << 8 | p; break;
+    case 1:
+      rgb = q << 16 | v << 8 | p; break;
+    case 2:
+      rgb = p << 16 | v << 8 | t; break;
+    case 3:
+      rgb = p << 16 | q << 8 | v; break;
+    case 4:
+      rgb = t << 16 | p << 8 | v; break;
+    default:
+      rgb = v << 16 | p << 8 | q; break;
+  }
+}
+
+void rgb2hsv(const uint32_t rgb, CHSV32& hsv) // convert RGB to HSV (16bit hue), much more accurate and faster than fastled version
+{
+    hsv.raw = 0;
+    int32_t r = (rgb>>16)&0xFF;
+    int32_t g = (rgb>>8)&0xFF;
+    int32_t b = rgb&0xFF;
+    int32_t minval, maxval, delta;
+    minval = min(r, g);
+    minval = min(minval, b);
+    maxval = max(r, g);
+    maxval = max(maxval, b);
+    if (maxval == 0)  return; // black
+    hsv.v = maxval;
+    delta = maxval - minval;
+    hsv.s = (255 * delta) / maxval;
+    if (hsv.s == 0)  return; // gray value
+    if (maxval == r) hsv.h = (10923 * (g - b)) / delta;
+    else if (maxval == g)  hsv.h = 21845 + (10923 * (b - r)) / delta;
+    else hsv.h = 43690 + (10923 * (r - g)) / delta;
+}
+
+void colorHStoRGB(uint16_t hue, byte sat, byte* rgb) { //hue, sat to rgb
+  uint32_t crgb;
+  hsv2rgb(CHSV32(hue, sat, 255), crgb);
+  rgb[0] = byte((crgb) >> 16);
+  rgb[1] = byte((crgb) >> 8);
+  rgb[2] = byte(crgb);
 }
 
 //get RGB values from color temperature in K (https://tannerhelland.com/2012/09/18/convert-temperature-rgb-algorithm-code.html)