Added ColorSensor.lab(), hsv() and hls() (#417)

Author: dwalton76

ev3dev/sensor/lego.py

@@ -261,6 +261,124 @@ def rgb(self):
                 min(int((green * 255) / self.green_max), 255),
                 min(int((blue * 255) / self.blue_max), 255))
 
+    @property
+    def lab(self):
+        """
+        Return colors in Lab color space
+        """
+        RGB = [0, 0, 0]
+        XYZ = [0, 0, 0]
+
+        for (num, value) in enumerate(self.rgb):
+            if value > 0.04045:
+                value = pow(((value + 0.055) / 1.055), 2.4)
+            else:
+                value = value / 12.92
+
+            RGB[num] = value * 100.0
+
+        # http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html
+        # sRGB
+        # 0.4124564  0.3575761  0.1804375
+        # 0.2126729  0.7151522  0.0721750
+        # 0.0193339  0.1191920  0.9503041
+        X = (RGB[0] * 0.4124564) + (RGB[1] * 0.3575761) + (RGB[2] * 0.1804375)
+        Y = (RGB[0] * 0.2126729) + (RGB[1] * 0.7151522) + (RGB[2] * 0.0721750)
+        Z = (RGB[0] * 0.0193339) + (RGB[1] * 0.1191920) + (RGB[2] * 0.9503041)
+
+        XYZ[0] = X / 95.047   # ref_X =  95.047
+        XYZ[1] = Y / 100.0    # ref_Y = 100.000
+        XYZ[2] = Z / 108.883  # ref_Z = 108.883
+
+        for (num, value) in enumerate(XYZ):
+            if value > 0.008856:
+                value = pow(value, (1.0 / 3.0))
+            else:
+                value = (7.787 * value) + (16 / 116.0)
+
+            XYZ[num] = value
+
+        L = (116.0 * XYZ[1]) - 16
+        a = 500.0 * (XYZ[0] - XYZ[1])
+        b = 200.0 * (XYZ[1] - XYZ[2])
+
+        L = round(L, 4)
+        a = round(a, 4)
+        b = round(b, 4)
+
+        return (L, a, b)
+
+    @property
+    def hsv(self):
+        """
+        HSV: Hue, Saturation, Value
+        H: position in the spectrum
+        S: color saturation ("purity")
+        V: color brightness
+        """
+        (r, g, b) = self.rgb
+        maxc = max(r, g, b)
+        minc = min(r, g, b)
+        v = maxc
+
+        if minc == maxc:
+            return 0.0, 0.0, v
+
+        s = (maxc-minc) / maxc
+        rc = (maxc-r) / (maxc-minc)
+        gc = (maxc-g) / (maxc-minc)
+        bc = (maxc-b) / (maxc-minc)
+
+        if r == maxc:
+            h = bc-gc
+        elif g == maxc:
+            h = 2.0+rc-bc
+        else:
+            h = 4.0+gc-rc
+
+        h = (h/6.0) % 1.0
+
+        return (h, s, v)
+
+    @property
+    def hls(self):
+        """
+        HLS: Hue, Luminance, Saturation
+        H: position in the spectrum
+        L: color lightness
+        S: color saturation
+        """
+        (r, g, b) = self.rgb
+        maxc = max(r, g, b)
+        minc = min(r, g, b)
+        l = (minc+maxc)/2.0
+
+        if minc == maxc:
+            return 0.0, l, 0.0
+
+        if l <= 0.5:
+            s = (maxc-minc) / (maxc+minc)
+        else:
+            if 2.0-maxc-minc == 0:
+                s = 0
+            else:
+                s = (maxc-minc) / (2.0-maxc-minc)
+
+        rc = (maxc-r) / (maxc-minc)
+        gc = (maxc-g) / (maxc-minc)
+        bc = (maxc-b) / (maxc-minc)
+
+        if r == maxc:
+            h = bc-gc
+        elif g == maxc:
+            h = 2.0+rc-bc
+        else:
+            h = 4.0+gc-rc
+
+        h = (h/6.0) % 1.0
+
+        return (h, l, s)
+
     @property
     def red(self):
         """