Implement support for shim avatar display

snikket_web/colour.py

@@ -0,0 +1,32 @@
+import functools
+import hashlib
+
+import hsluv
+
+# This is essentially an implementation of XEP-0392.
+
+
+def clip_rgb(r, g, b):
+    return (
+        min(max(r, 0), 1),
+        min(max(g, 0), 1),
+        min(max(b, 0), 1),
+    )
+
+
+@functools.lru_cache(128)
+def text_to_colour(text):
+    MASK = 0xffff
+    h = hashlib.sha1()
+    h.update(text.encode("utf-8"))
+    hue = (int.from_bytes(h.digest()[:2], "little") & MASK) / MASK
+    r, g, b = hsluv.hsluv_to_rgb((hue * 360, 75, 60))
+    # print(text, cb, cr, r, g, b)
+    r, g, b = clip_rgb(r, g, b)
+    return r, g, b
+
+
+def text_to_css(text):
+    return "#{:02x}{:02x}{:02x}".format(
+        *(round(v * 255) for v in text_to_colour(text))
+    )