implement proper white channel calculation

src/main.cpp

@@ -36,7 +36,7 @@
 const uint16_t 
 	Num_Leds   =  264;         // strip length
 const uint8_t
-	Brightness =  100;        // maximum brightness
+	Brightness =  127;        // maximum brightness
 
 // --- FastLED Setings
 #if defined(SK6812RGBW)
@@ -273,10 +273,30 @@ void dataMode(){
 				uint8_t r=leds[i].r;
 				uint8_t g=leds[i].g;
 				uint8_t b=leds[i].b;
+
+				/* Simple 255,255,255 = White approach
 				uint8_t w=min(r,min(g,b)); //get white content and use for white
 				r-=w; //subtract white content
 				g-=w;
 				b-=w;
+				*/
+
+				// Calibration 20201207. These RGB values match the Neutral White color with calibW brightness.
+				uint8_t calibR=255;
+				uint8_t calibG=175;
+				uint8_t calibB=90;
+				uint8_t calibW=135;
+				
+				//one of calibR,calibG or calibB should be 255.
+				int minval=min(r-calibR,min(g-calibG,b-calibB)); //0 if rgb contains full white. <0 if not full white. -1*(max(calibR,calibG,calibB)) if no white content
+				float whitecontent=1.0 + (minval/255.0);  //scale to: 0=no white, 1=full white content
+				//subtract white contents from rgb
+				r-=calibR*whitecontent;
+				g-=calibG*whitecontent;
+				b-=calibB*whitecontent;
+
+				uint8_t w=calibW*whitecontent;
+
 
 				send_leds[i] = CRGBW(r, g, b, w); //transfer to rgbw struct
 			}