Does using "optimize PNG" in SLADE decrease sprite/texture quality in some noticeable way?

[LukeGaming]

So I downloaded these three programs for SLADE

And using that option usually decreases filesize about 50% (to be honest I don't know what these programs do to achive that)

And sprites look pretty much the same to me despite heavily reduced filesize, does anyone else who uses these programs has noticed any decrease in quality?

Edited October 18, 2023 by LukeGaming

[Blzut3]

There is no quality loss.  There are many bit streams which are valid representations of the same image, but finding the optimal one is a very computationally expensive task which quickly diminishing returns.  For things you're actively working on it makes sense to strike a balance between file size and speed of compression, but when you're done you can do an optimization pass to compress things further.

 

Those tools do also remove some meta data which doesn't affect the rendered image.  What that meta data is and why it exists varies between applications/use cases, but Slade would invoke those tools in a way to leave the bits relevant to Doom alone.

 

For completeness I will note that there do exist tools like pngquant which can use lossy techniques to compress PNGs further with some quality loss, but the ones in question don't.

[LukeGaming]

2 hours ago, Blzut3 said:

Those tools do also remove some meta data which doesn't affect the rendered image.  What that meta data is and why it exists varies between applications/use cases, but Slade would invoke those tools in a way to leave the bits relevant to Doom alone.

 

Thank you for explanation.