From 868112ca976877889e2c6ff97d052737e8d0e163 Mon Sep 17 00:00:00 2001
From: Dre Westcook <dre.westcook@octoenergy.com>
Date: Sat, 13 Jan 2024 07:10:14 +1100
Subject: [PATCH] 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 | 15 +++++++++------
 tests/test_ffmpeg_reader.py       | 16 ++++++++++++++++
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/moviepy/video/io/ffmpeg_reader.py b/moviepy/video/io/ffmpeg_reader.py
index b7be97177..5e6ce5bac 100644
--- a/moviepy/video/io/ffmpeg_reader.py
+++ b/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
diff --git a/tests/test_ffmpeg_reader.py b/tests/test_ffmpeg_reader.py
index f01127b73..4fc9749bb 100644
--- a/tests/test_ffmpeg_reader.py
+++ b/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)