Bugfix: Allow using #hex colors with 3 characters (#998)

* Fix error using #hex colors with 3 characters

* Add test

Author: mondeja

manim/utils/color.py

@@ -289,7 +289,7 @@ def rgb_to_hex(rgb):
 def hex_to_rgb(hex_code):
     hex_part = hex_code[1:]
     if len(hex_part) == 3:
-        "".join([2 * c for c in hex_part])
+        hex_part = "".join([2 * c for c in hex_part])
     return np.array([int(hex_part[i : i + 2], 16) / 255 for i in range(0, 6, 2)])
 
 

tests/test_color.py

@@ -20,6 +20,10 @@ def test_background_color():
     S.renderer.update_frame(S)
     assert np.all(S.renderer.get_frame()[0, 0] == np.array([67, 111, 128, 255]))
 
+    S.camera.background_color = "#fff"
+    S.renderer.update_frame(S)
+    assert np.all(S.renderer.get_frame()[0, 0] == np.array([255, 255, 255, 255]))
+
     S.camera.background_color = "#bbffbb"
     S.camera.background_opacity = 0.5
     S.renderer.update_frame(S)