Fix 'video.tools.drawing.color_gradient' (Zulko#1467)

* Fix inconsistency of arguments in 'video.tools.drawing.color_gradient'

* Add CHANGELOG entry

* Fix error in implementation

* Fix formatting error

* Remove uneeded lines

* Remove uneeded if

* Raise ValueError if 'shape' is invalid

* Raise 'ValueError' with inconsistent p2/vector in 'bilinear' shape

CHANGELOG.md

@@ -37,6 +37,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed `freeze` FX was freezing at time minus 1 second as the end [\#1461](https://github.com/Zulko/moviepy/pull/1461)
 - `AudioClip.max_volume(stereo=True)` now can return more than 2 channels [\#1464](https://github.com/Zulko/moviepy/pull/1464)
 - Fixed `Clip.cutout` transformation not being applied to audio [\#1468](https://github.com/Zulko/moviepy/pull/1468)
+- Fixed arguments inconsistency in `video.tools.drawing.color_gradient` [\#1467](https://github.com/Zulko/moviepy/pull/1467)
 
 
 ## [v2.0.0.dev2](https://github.com/zulko/moviepy/tree/v2.0.0.dev2) (2020-10-05)

moviepy/video/tools/drawing.py

@@ -102,6 +102,8 @@ def color_gradient(
 
     if shape == "bilinear":
         if vector is None:
+            if p2 is None:
+                raise ValueError("You must provide either 'p2' or 'vector'")
             vector = np.array(p2) - np.array(p1)
 
         m1, m2 = [
@@ -124,20 +126,18 @@ def color_gradient(
 
     p1 = np.array(p1[::-1]).astype(float)
 
-    if vector is None and p2:
-        p2 = np.array(p2[::-1])
-        vector = p2 - p1
-    else:
-        vector = np.array(vector[::-1])
-        p2 = p1 + vector
-
-    if vector is not None:
-        norm = np.linalg.norm(vector)
-
     M = np.dstack(np.meshgrid(range(w), range(h))[::-1]).astype(float)
 
     if shape == "linear":
+        if vector is None:
+            if p2 is not None:
+                vector = np.array(p2[::-1]) - p1
+            else:
+                raise ValueError("You must provide either 'p2' or 'vector'")
+        else:
+            vector = np.array(vector[::-1])
 
+        norm = np.linalg.norm(vector)
         n_vec = vector / norm ** 2  # norm 1/norm(vector)
 
         p1 = p1 + offset * vector
@@ -148,10 +148,7 @@ def color_gradient(
         return arr * color_1 + (1 - arr) * color_2
 
     elif shape == "radial":
-        if radius is None:
-            radius = norm
-
-        if radius == 0:
+        if (radius or 0) == 0:
             arr = np.ones((h, w))
         else:
             arr = (np.sqrt(((M - p1) ** 2).sum(axis=2))) - offset * radius
@@ -161,6 +158,7 @@ def color_gradient(
         if color_1.size > 1:
             arr = np.dstack(3 * [arr])
         return (1 - arr) * color_1 + arr * color_2
+    raise ValueError("Invalid shape, should be either 'radial', 'linear' or 'bilinear'")
 
 
 def color_split(