Fix target resolution specification

When only one dimension was specified in the target resolution it was
used to find the scale factor, then used to scale the video with a
possible rounding issue, causing a mismatch between what was given and
what was received.

This change will only calculate the unspecified dimension and use the
given value as is.

moviepy/video/io/ffmpeg_reader.py

@@ -43,13 +43,16 @@ def __init__(
  if self.rotation in [90, 270]:
  self.size = [self.size[1], self.size[0]]
 
- if target_resolution:
+ if target_resolution and target_resolution != (None, None):
  if None in target_resolution:
- ratio = 1
- for idx, target in enumerate(target_resolution):
- if target:
- ratio = target / self.size[idx]
- self.size = (int(self.size[0] * ratio), int(self.size[1] * ratio))
+ first, second = target_resolution
+ if first:
+ ratio = first / self.size[0]
+ second = int(self.size[1] * ratio)
+ else:
+ ratio = second / self.size[1]
+ first = int(self.size[0] * ratio)
+ self.size = (first, second)
  else:
  self.size = target_resolution
  self.resize_algo = resize_algo

tests/test_ffmpeg_reader.py

@@ -290,6 +290,22 @@ def test_ffmpeg_parse_video_rotation():
  assert d["video_size"] == [1920, 1080]
 
 
+@pytest.mark.parametrize(
+ "target_resolution,expected_size",
+ [
+ (None, (314, 273)),
+ ((100, None), (100, 86)),
+ ((None, 100), (115, 100)),
+ ((None, None), (314, 273)),
+ ],
+)
+def test_video_target_resolution(target_resolution, expected_size):
+ clip = VideoFileClip(
+ "media/pigs_in_a_polka.gif", target_resolution=target_resolution
+ )
+ assert clip.size == expected_size
+
+
 def test_correct_video_rotation(util):
  """See https://github.com/Zulko/moviepy/pull/577"""
  clip = VideoFileClip("media/rotated-90-degrees.mp4").subclip(0.2, 0.4)