add support for color_temp

Author: cribbstechnologies

Diff for: ESP_MQTT_Digital_LEDs/ESP_MQTT_Digital_LEDs.ino

@@ -381,6 +381,15 @@ bool processJson(char* message) {
       green = root["color"]["g"];
       blue = root["color"]["b"];
     }
+    
+    if (root.containsKey("color_temp")) {
+      //temp comes in as mireds, need to convert to kelvin then to RGB
+      int color_temp = root["color_temp"];
+      unsigned int kelvin  = MILLION / color_temp;
+      
+      temp2rgb(kelvin);
+      
+    }
 
     if (root.containsKey("brightness")) {
       brightness = root["brightness"];
@@ -1046,3 +1055,57 @@ void showleds() {
     startFade = false;
   }
 }
+void temp2rgb(unsigned int kelvin) {
+    int tmp_internal = kelvin / 100.0;
+    
+    // red 
+    if (tmp_internal <= 66) {
+        red = 255;
+    } else {
+        float tmp_red = 329.698727446 * pow(tmp_internal - 60, -0.1332047592);
+        if (tmp_red < 0) {
+            red = 0;
+        } else if (tmp_red > 255) {
+            red = 255;
+        } else {
+            red = tmp_red;
+        }
+    }
+    
+    // green
+    if (tmp_internal <=66){
+        float tmp_green = 99.4708025861 * log(tmp_internal) - 161.1195681661;
+        if (tmp_green < 0) {
+            green = 0;
+        } else if (tmp_green > 255) {
+            green = 255;
+        } else {
+            green = tmp_green;
+        }
+    } else {
+        float tmp_green = 288.1221695283 * pow(tmp_internal - 60, -0.0755148492);
+        if (tmp_green < 0) {
+            green = 0;
+        } else if (tmp_green > 255) {
+            green = 255;
+        } else {
+            green = tmp_green;
+        }
+    }
+    
+    // blue
+    if (tmp_internal >=66) {
+        blue = 255;
+    } else if (tmp_internal <= 19) {
+        blue = 0;
+    } else {
+        float tmp_blue = 138.5177312231 * log(tmp_internal - 10) - 305.0447927307;
+        if (tmp_blue < 0) {
+            blue = 0;
+        } else if (tmp_blue > 255) {
+            blue = 255;
+        } else {
+            blue = tmp_blue;
+        }
+    }
+}