[PYTHON] Make a GIF animation with folder monitoring

Why GIF animation

If you are developing smartphone apps or front-ends, you may want to post a video on Issues or Pull requests on Github. However, it does not support uploading video files such as mp4. I get an error like this when I try to upload an mp4 file.

However, it does support uploading GIF files, and GIF has an animation function. There are some compromises in image quality, such as up to 256 colors, but you can use them to post videos.

Why folder monitoring

I usually develop Android apps, but I felt inefficient in the current GIF animation creation process. (The process is based on Mac)

** Process 1 ** Record the screen of the Android device

1. Click the tab under Logcat in Android Studio
2. Check if Logcat of the terminal to record is displayed
3. Click the Screen Record button at the bottom left of Logcat
4. Click the Start Recording button

For command line people, see the supplement.

** Step 2 ** Save the mp4 format file

1. Select a save folder
2. Set the file name as needed
3. Click the Save button

** Step 3 ** Encode to GIF animation format.

Convert mp4 file to gif file with ffmepg command. Since Github has a 10MB limit for uploaded images, the width is 320px and 10fps to reduce the capacity.

ffmpeg -i input.mp4 -vf scale=320:-1 -r 10 output.gif

** Process 4 ** Upload to Github

You can upload a GIF animation by dragging and dropping it into the comment input field on Github.

Efficiency

If you monitor the folder, the process-File saving can be used as a trigger to automatically encode to GIF animation format, which makes your work more efficient.

Monitor folders

I created a Python program like this.

watch.py

import os
import time
from watchdog.events import FileSystemEventHandler
from watchdog.events import FileCreatedEvent
from watchdog.observers import Observer
from pathlib import PurePath
import subprocess
import signal


class MovieFileSystemEventHandler(FileSystemEventHandler):

    def on_any_event(self, event):
        if(type(event) == FileCreatedEvent):
            src_path = event.src_path
            pp = PurePath(src_path)
            if pp.suffix != '.gif':
                output_path = "%s/%s.gif" % (os.path.dirname(src_path), pp.stem)
                subprocess.run(['ffmpeg', '-i', event.src_path, '-vf',
                                'scale=320:-1', '-r', '10', output_path])


exit_flag = False


def handle_exit(sig, frame):
    global exit_flag
    exit_flag = True


signal.signal(signal.SIGINT, handle_exit)
signal.signal(signal.SIGTERM, handle_exit)


path = "%s/movie" % os.environ['HOME']
event_handler = MovieFileSystemEventHandler()
observer = Observer()
observer.schedule(event_handler, path, recursive=True)
observer.start()
while exit_flag == False:
    time.sleep(1)

observer.stop()
observer.join()

This program uses a library called Watchdog, so install it with the pip command.

pip install watchdog

This program also monitors ~ / movie and saves the encoded gif animation in the same location, but if you prefer a different folder, rewrite this part if you like.

path = "%s/movie" % os.environ['HOME']

Create a monitoring folder.

mkdir ~/movie

Run a Python program. It will be a resident program.

python watchdog.py

This will monitor the folder. If the video file is saved in the watch folder, a gif animation file with the same name will be automatically generated.

To end the resident, press Ctrl + C on the console.

Supplement

Install ffmpeg

You can install it using brew.

brew install ffmpeg

Record Android screen from command line

adb shell
adb /mnt/sdcard
#Start recording
screenrecord output.mp4
# Ctrl +End recording with C
exit
adb pull /mnt/sdcard/output.mp4

Precautions when converting to Docker

Docker conversion is also possible. However, there are cases where it does not work properly. Saving directly from Android Studio to the monitoring directory is fine, but moving from another folder did not work properly.

FROM python:3.7-alpine
WORKDIR /root/
RUN apk add --update --no-cache ffmpeg
RUN pip install watchdog
COPY watch.py .
CMD python watch.py

docker-compose.yml

version: '3'
services:
    main:
        build: .
        volumes:
            - ~/movie:/root/movie

Build and run.

docker-compose build
docker-compose up

Details of cases that do not work properly

class MovieFileSystemEventHandler(FileSystemEventHandler):

    def on_any_event(self, event):
        # type(event)To confirm

When I moved a file from another folder to a watch folder, I got a FileModifiedEvent instead of a FileCreatedEvent. I also wanted to convert the video to GIF animation with FileModifiedEvent, but when copying from another folder, FileModifiedEvent occurs after FileCreatedEvent, and I thought it would be difficult to create an appropriate trigger.