Revert "[Misc] Improve gif output compression rate" (taichi-dev#6517)

Reverts taichi-dev#6289

python/taichi/tools/video.py

@@ -1,6 +1,7 @@
 import os
 import shutil
 
+from taichi._lib.utils import get_os_name
 from taichi.tools.image import imwrite
 
 FRAME_FN_TEMPLATE = '%06d.png'
@@ -31,18 +32,25 @@ def get_ffmpeg_path():
     return 'ffmpeg'
 
 
-def mp4_to_gif(input_fn, output_fn, framerate, **kwargs):
-    try:
-        from moviepy.editor import \
-            VideoFileClip  # pylint: disable=import-outside-toplevel
-    except:
-        raise ImportError(
-            "'moviepy' is required to process video files, please run 'pip install moveipy' to install it first."
-        )
-
-    clip = VideoFileClip(input_fn)
-    prog = get_ffmpeg_path()
-    clip.write_gif(output_fn, fps=framerate, program=prog, **kwargs)
+def mp4_to_gif(input_fn, output_fn, framerate):
+    # Generate the palette
+    palette_name = 'palette.png'
+    if get_os_name() == 'win':
+        command = get_ffmpeg_path(
+        ) + f" -loglevel panic -i {input_fn} -vf 'palettegen' -y {palette_name}"
+    else:
+        command = get_ffmpeg_path(
+        ) + f" -loglevel panic -i {input_fn} -vf 'fps={framerate}," \
+            f"scale=320:640:flags=lanczos,palettegen' -y {palette_name}"
+    # print command
+    os.system(command)
+
+    # Generate the GIF
+    command = get_ffmpeg_path(
+    ) + f" -loglevel panic -i {input_fn} -i {palette_name} -lavfi paletteuse -y {output_fn}"
+    # print command
+    os.system(command)
+    os.remove(palette_name)
 
 
 class VideoManager: