Support PIL images as image source

[falkoschindler]

Following up on feature request #2067, this PR adds support for PIL images as source for ui.image and ui.interactive_image. Note that changing the image programmatically via value = ... or set_value(...) is handled as well.

I'm just not sure if this is the right approach, because we implicitly define the image format to be PNG, and I'm not sure if we benefit from ZIP compression when sending the image content as byte string instead of serving an image file instead.

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• make image format a static constant in ui.image.

[nghia-vo]

How to control the size of a displayed image? Something similar to ui.pyplot(figsize=)

[rodja]

we implicitly define the image format to be PNG

I think that is ok. Users needing JPEG or something else could use the image_to_base64 function instead of relying on the automatism.

and I'm not sure if we benefit from ZIP compression

Well, this suboptimal. Similar to ui.download the data is send through a websocket event which we do not compress. But that should be worth another pull request in my opinion.

How to control the size of a displayed image? Something similar to ui.pyplot(figsize=)

The physical size of the image can be changed by applying resize operations on the PIL Image before passing into ui.image. And the display size is controlled with css and Tailwind. No need for another parameter.