What happens when you compress a compressed PNG?

[Hamzer the Conqueror (of lands)]

Say I save a blender render as a 100% compressed PNG and then opened it in some image editing software and re compressed it. Does it make the file size smaller?

[RGX12]

It cannot be made smaller just by re-saving it, assuming identical image specs. However, by reducing color bit-depth, and playing with a few other parameters, the file size can (usually) be reduced. There is a program, TinyPNG, which can automate this for you:
https://tinypng.com

[Bad 💀 Motha]

Why are you compressing at all; leave it as original quality lossless PNG
Unless you're doing like 8K+ for the res, then the files shouldn't be that big anyways.

[Astraea Kisaragi]

PNG generally suffers less when is sized down. Its slightly blurs but it has no artefacts like JPG does.

[Hamzer the Conqueror (of lands)]

Bad_Motha a écrit :

Why are you compressing at all; leave it as original quality lossless PNG
Unless you're doing like 8K+ for the res, then the files shouldn't be that big anyways.

Compressing a PNG is a lossless process. It just takes longer to process