new example: ffmpeg image extractor

examples/ffmpeg_extract_images/main.py

@@ -0,0 +1,48 @@
+#!/usr/bin/env python3
+import asyncio
+import os
+import pathlib
+import shlex
+import shutil
+import subprocess
+from concurrent.futures import ProcessPoolExecutor
+
+from icecream import ic
+
+from nicegui import app, events, ui
+
+
+def extract(source: str):
+    subprocess.call(shlex.split(f'ffmpeg -i "{source}" -vf fps=1 out_%04d.jpg'))
+
+
+async def handle_upload(args: events.UploadEventArguments):
+    ic()
+    if 'video' in args.type:
+        shutil.rmtree('data', ignore_errors=True)
+        os.makedirs('data', exist_ok=True)
+        os.chdir('data')
+        with open(args.name, 'wb') as f:
+            f.write(args.content.read())
+            results.clear()
+            with results:
+                ui.spinner('dots', size='xl')
+            await asyncio.to_thread(extract, args.name)
+            results.clear()
+            with results:
+                for path in pathlib.Path('.').glob('*.jpg'):
+                    ui.image(f'/data/{path.name}').classes('w-96 drop-shadow-md rounded')
+        os.chdir('..')
+    else:
+        ui.notify('Please upload a video file')
+    upload.run_method('reset')
+
+
+app.add_static_files('/data', 'data')
+
+with ui.column().classes('w-full items-center'):
+    ui.label('Extract images from video').classes('text-3xl m-3')
+    upload = ui.upload(label='pick a video file', auto_upload=True, on_upload=handle_upload)
+    results = ui.row().classes('w-full justify-center mt-6')
+
+ui.run()