First, irfanview (4.54 32bit on WinXP) cannot view the picture in forum's registration process:
https://irfanview-forum.de/attachmen...034821&thumb=1
It shows all black.

Then, the two test image:
https://www.w3.org/Graphics/PNG/all_seven.html
gamma info is not processed.

https://www.w3.org/Graphics/PNG/inline-alpha.html
alpha info is not processed? Maybe it just used black as background, so I'm not sure if it is a bug or not, just bringing to your attention.