allow quality argument to be passed to save

[jamarju]

No description provided.

[Isotr0py]

Thanks for your contribution!

Note that the quality used in jpegxl-rs is the FrameDistance in libjxl in fact, which ranges from 0 .. 25 and lower = higher quality.

I'm afraid that if we just expose quality simply, this may cause a confusing situation. Because a JPEG-style quality factor usually ranges up to 100 and higher = higher quality.

For example, if user mistakes the quality here is the JPEG-style one, and then:

with Image.open("1.png") as im:
    im.save("1.jxl", quality=98)

This will cause a confusing panic in Rust binding:

PanicException: called `Result::unwrap()` on an `Err` value: ApiUsage

[jamarju]

I added a mapping according to aforementioned function, take a look and let me know what you think. Might be even cleaner to call the native function from the rust side of the code?

[Isotr0py]

LGTM.

I will update the forked jpegxl-rs with JxlEncoderDistanceFromQuality and submit a PR to jpegxl-rs main repo for further refinement in the near future.