Async support?

[rushkii]

Do you have any plan to make another Pillow with async support?

[radarhere]

Hi. There are no current plans.

I would have thought that the end user could just wrap calls to Pillow within their own async code.

Can you give an example of something that is better implemented within Pillow, rather than the end user's code?

[cdgriffith]

A pretty straightforward example would be use in very asyncio heavy libraries like FastAPI. When using pillow to create thumbnails, would be great to simply be able to await the open / save tasks. Currently they have to be put into a background thread so they don't block the webserver.

[radarhere]

I've not experimented with asyncio myself, so bear with me - but if you want to await an open(), is it not as simple as this?

from PIL import Image
import asyncio

async def image_open(path):
    return Image.open(path)

async def main():
    im = await image_open("hopper.png")
    print(im)

asyncio.run(main())

[wiredfool]

Yes, but it would suck. Especially when the deferred load gets called.

My understanding of async is that you might yield control to alternate "threads" anywhere there is an await, and that what runs within that async will be scheduled "sometime" when something else potentially yields.

To make this work, you basically need async all the way down, otherwise you're going to wind up blocking everyone else when you do something that takes a significant amount of time, like waiting for disk IO in Image.open, or pixel unpacking in load, or encoding in save. Async IO all the way down is going to be difficult, as we don't always control the IO primitives. If your image op takes 100ms and you've done this in an async context without some form of worker thread, then you're going to have a 100ms latency pause in all of the other concurrent operations.

So essentially, we'd have to setup a worker thread pool for everything that will potentially take time and ensure that it's used for those operations.

[PogoDigitalism]

A bit late but, I have an open repository called PillowInAsync .

(check the examples folder for diffferent applications of the technique)

I use a thread pool executor with Async IO tasks to make my Pillow image generation work with Async projects such as discord.py. 👍

I have now added a user-friendly copy-paste class to SyncInAsync to run synchronous functions in async environments!

[aclark4life]

Nice!