Added ImageOps contain()

[radarhere]

Resolves #5415

Adds a contain() method to ImageOps. I would describe it as the inverse of fit().

Running this code for each method in turn for comparison -

from PIL import Image, ImageOps
im = Image.open("Tests/images/hopper.png")
ImageOps.fit(im, (200, 300))

	Fit	Pad	Contain
Size	200 x 300	200 x 300	200 x 200
Image

[radarhere]

3.10-dev failures seem to be due to pytest-dev/pytest#8539, which has been resolved, but is not available in a pytest release yet.

[axu2]

Looks great, exactly what I was looking for.

[axu2]

Sorry, I left a bunch of comments that I quickly deleted, since I had made an error. I was using a super old version of Pillow using Python2 but Python3 was fine. Seems like ImageOps.pad was always broken on Python2.

[hugovk]

Let's also include this in the docs (autofunction in docs/reference/ImageOps.rst?) and release notes.

[hugovk]

Thank you!

[axu2]

🥳

[axu2]

Oh one last comment, just realized this function is similar to Image.thumbnail except it will upscale the image, if needed.

Also, for upscaling low resolution text, NEAREST might be a better choice.
https://en.wikipedia.org/wiki/Comparison_gallery_of_image_scaling_algorithms
Not a big deal though, since I can specify the method if I want, and bicubic is probably a better default for every other use case.

EDIT: nvm, just tested, NEAREST looks terrible for my use case haha.