Image.MIME populated unexpectedly

[cjuracek]

What did you do?

Attempt to get mapping from MIME type to PIL format via PIL.Image.MIME

What did you expect to happen?

A filled dictionary mapping from MIME type to PIL format.

What actually happened?

Empty dict. It looks like PIL.Image.init() populates this registry.

It's understandable if this method needs to be called before the MIME registry is populated. But some documentation surrounding this and the MIME variable would be useful. I was especially surprised when PIL.features.pilinfo() populated this variable as a side effect.

What are your OS, Python and Pillow versions?

• OS: macOS Monterey 12.6.8
• Python: 3.8.15
• Pillow: 10.0.0

if __name__ == "__main__":
    print(f"PIL.Image.MIME before pilinfo(): {Image.MIME}")
    features.pilinfo()
    print(f"PIL.Image.MIME after pilinfo(): {Image.MIME}")

[radarhere]

What do you think of #7399? With it, you should be able to go to the documentation for the Image module, search for "MIME" and find this screen telling you everything you need to know -

• register_mime() tells you that it populates Image.MIME
• The 'Note' tells you that register_mime() is called by preinit() or init()
• init() tells you that it is called when opening, saving or by features.pilinfo()

[cjuracek]

That looks good - maybe better documentation on this was all I was looking for.