Fixes #2504 in artresizer

[architek]

This PR fixes #2504

PIL Image.save() requires a string parameter [1] while with python3 we call it with bytes.
This leads to wrong format detection (b'.png' isn't a key in supported formats list whereas '.png' is).

I haven't found a better existing function to do this (feel free to change patch) nor a unit test using PIL Image.save.

[1] https://pillow.readthedocs.io/en/latest/reference/Image.html#PIL.Image.Image.save

[sampsyo]

Cool! Thanks for looking into this.

displayable_path, however, is a lossy function that is just for printing out paths for human consumption. Can you please try our py3_path utility function, which is just for these poorly-behaved libraries that demand Unicode paths?

[architek]

I've updated the PR to use py3_path
Thank you

[sampsyo]

Great! And just to check what should probably be obvious: have you tried this latest version of the change out on Python? Which Python version? Did it work on an example that it previously didn’t work for?

[architek]

Sure I did test that.

But your question was a good opportunity to install and test with python 3.7 ;-)

In the end, using 2.7, 3.5 and 3.7 (ImageMagick not installed), I can confirm that:

• KeyError bug when resizing images exists with 3.5 and 3.7,
• It is not present anymore after using py3_path,
• Using 2.7, still works fine

For reference, Python Image Library is Pillow 5.2.0.

Thank you

[sampsyo]

That is awesome! Thank you for the exhaustive testing! ✨ I'll merge this now. 🚀