A PNG with transparency gets incorrectly rendered

[rec]

Most PNG files don't exhibit this, but I have one lying around that has a lot of transparency and does.

/code/env/hardback/lib/python3.6/site-packages/PIL/Image.py:966: UserWarning: Palette images with Transparency expressed in bytes should be converted to RGBA images

'to RGBA images'

The result is wrong colors (green background in a black-only image) and pixelated edges - see attached PNG.

Workaround - don't use one-color PNG images with transparency.

[rec]

This was the same image as in #3.