diff --git a/hsv2rgbw.py b/hsv2rgbw.py
new file mode 100644
index 0000000..5d510ad
--- /dev/null
+++ b/hsv2rgbw.py
@@ -0,0 +1,43 @@
+import numpy as np
+
+# h = 0..359
+# s = 0..255
+# v = 0..511 (values above 255 add white channel)
+def hsv2rgbw(h, s, v):
+
+    h %= 360
+
+    v_ = min(255, v)
+
+    # C = 0..255
+    C = (v_ * s) // 256
+
+    h_ = 128 * h // 60
+
+    # X = 0..255
+    X = C * (128 - abs(h_ % 256 - 128)) // 128
+
+    if h < 60:
+        r, g, b = C, X, 0
+    elif h < 120:
+        r, g, b = X, C, 0
+    elif h < 180:
+        r, g, b = 0, C, X
+    elif h < 240:
+        r, g, b = 0, X, C
+    elif h < 300:
+        r, g, b = X, 0, C
+    else:
+        r, g, b = C, 0, X
+
+    m = v_ - C
+    r += m
+    g += m
+    b += m
+
+    if v >= 256:
+        w = v - 255
+    else:
+        w = 0
+
+    return np.array([r, g, b, w])