Change color_RGB_to_xy formula & return brightness (#2095)

* Use RGB to XY calculations from Philips Hue developer site

* uppercase X,Y,Z

* rename cx,cy to x,y

* return brightness in color_RGB_to_xy

* remove try/catch

* update existing platforms using color_RGB_to_xy

* improve wemo w/ jaharkes suggestion

* allow brightness override of rgb_to_xy

homeassistant/components/light/hue.py

@@ -235,14 +235,16 @@ class HueLight(Light):
         if ATTR_TRANSITION in kwargs:
             command['transitiontime'] = kwargs[ATTR_TRANSITION] * 10
 
-        if ATTR_BRIGHTNESS in kwargs:
-            command['bri'] = kwargs[ATTR_BRIGHTNESS]
-
         if ATTR_XY_COLOR in kwargs:
             command['xy'] = kwargs[ATTR_XY_COLOR]
         elif ATTR_RGB_COLOR in kwargs:
-            command['xy'] = color_util.color_RGB_to_xy(
+            xyb = color_util.color_RGB_to_xy(
                 *(int(val) for val in kwargs[ATTR_RGB_COLOR]))
+            command['xy'] = xyb[0], xyb[1]
+            command['bri'] = xyb[2]
+
+        if ATTR_BRIGHTNESS in kwargs:
+            command['bri'] = kwargs[ATTR_BRIGHTNESS]
 
         if ATTR_COLOR_TEMP in kwargs:
             command['ct'] = kwargs[ATTR_COLOR_TEMP]

homeassistant/components/light/wemo.py

@@ -105,6 +105,7 @@ class WemoLight(Light):
         elif ATTR_RGB_COLOR in kwargs:
             xycolor = color_util.color_RGB_to_xy(
                 *(int(val) for val in kwargs[ATTR_RGB_COLOR]))
+            kwargs.setdefault(ATTR_BRIGHTNESS, xycolor[2])
         else:
             xycolor = None
 

homeassistant/components/light/wink.py

@@ -97,7 +97,9 @@ class WinkLight(Light):
         }
 
         if rgb_color:
-            state_kwargs['color_xy'] = color_util.color_RGB_to_xy(*rgb_color)
+            xyb = color_util.color_RGB_to_xy(*rgb_color)
+            state_kwargs['color_xy'] = xyb[0], xyb[1]
+            state_kwargs['brightness'] = xyb[2]
 
         if color_temp_mired:
             state_kwargs['color_kelvin'] = mired_to_kelvin(color_temp_mired)

homeassistant/util/color.py

@@ -7,44 +7,41 @@ HASS_COLOR_MAX = 500  # mireds (inverted)
 HASS_COLOR_MIN = 154
 
 
-# Taken from: http://www.cse.unr.edu/~quiroz/inc/colortransforms.py
+# Taken from:
+# http://www.developers.meethue.com/documentation/color-conversions-rgb-xy
 # License: Code is given as is. Use at your own risk and discretion.
 # pylint: disable=invalid-name
 def color_RGB_to_xy(R, G, B):
     """Convert from RGB color to XY color."""
     if R + G + B == 0:
-        return 0, 0
+        return 0, 0, 0
 
-    var_R = (R / 255.)
+    R = R / 255
-    var_G = (G / 255.)
+    B = B / 255
-    var_B = (B / 255.)
+    G = G / 255
 
-    if var_R > 0.04045:
+    # Gamma correction
-        var_R = ((var_R + 0.055) / 1.055) ** 2.4
+    R = pow((R + 0.055) / (1.0 + 0.055),
-    else:
+            2.4) if (R > 0.04045) else (R / 12.92)
-        var_R /= 12.92
+    G = pow((G + 0.055) / (1.0 + 0.055),
+            2.4) if (G > 0.04045) else (G / 12.92)
+    B = pow((B + 0.055) / (1.0 + 0.055),
+            2.4) if (B > 0.04045) else (B / 12.92)
 
-    if var_G > 0.04045:
+    # Wide RGB D65 conversion formula
-        var_G = ((var_G + 0.055) / 1.055) ** 2.4
+    X = R * 0.664511 + G * 0.154324 + B * 0.162028
-    else:
+    Y = R * 0.313881 + G * 0.668433 + B * 0.047685
-        var_G /= 12.92
+    Z = R * 0.000088 + G * 0.072310 + B * 0.986039
 
-    if var_B > 0.04045:
+    # Convert XYZ to xy
-        var_B = ((var_B + 0.055) / 1.055) ** 2.4
+    x = X / (X + Y + Z)
-    else:
+    y = Y / (X + Y + Z)
-        var_B /= 12.92
 
-    var_R *= 100
+    # Brightness
-    var_G *= 100
+    Y = 1 if Y > 1 else Y
-    var_B *= 100
+    brightness = round(Y * 255)
 
-    # Observer. = 2 deg, Illuminant = D65
+    return round(x, 3), round(y, 3), brightness
-    X = var_R * 0.4124 + var_G * 0.3576 + var_B * 0.1805
-    Y = var_R * 0.2126 + var_G * 0.7152 + var_B * 0.0722
-    Z = var_R * 0.0193 + var_G * 0.1192 + var_B * 0.9505
-
-    # Convert XYZ to xy, see CIE 1931 color space on wikipedia
-    return X / (X + Y + Z), Y / (X + Y + Z)
 
 
 # taken from

tests/util/test_color.py

@@ -9,16 +9,17 @@ class TestColorUtil(unittest.TestCase):
     # pylint: disable=invalid-name
     def test_color_RGB_to_xy(self):
         """Test color_RGB_to_xy."""
-        self.assertEqual((0, 0), color_util.color_RGB_to_xy(0, 0, 0))
+        self.assertEqual((0, 0, 0), color_util.color_RGB_to_xy(0, 0, 0))
-        self.assertEqual((0.3127159072215825, 0.3290014805066623),
+        self.assertEqual((0.32, 0.336, 255),
                          color_util.color_RGB_to_xy(255, 255, 255))
 
-        self.assertEqual((0.15001662234042554, 0.060006648936170214),
+        self.assertEqual((0.136, 0.04, 12),
                          color_util.color_RGB_to_xy(0, 0, 255))
 
-        self.assertEqual((0.3, 0.6), color_util.color_RGB_to_xy(0, 255, 0))
+        self.assertEqual((0.172, 0.747, 170),
+                         color_util.color_RGB_to_xy(0, 255, 0))
 
-        self.assertEqual((0.6400744994567747, 0.3299705106316933),
+        self.assertEqual((0.679, 0.321, 80),
                          color_util.color_RGB_to_xy(255, 0, 0))
 
     def test_color_xy_brightness_to_RGB(self):