This is an interesting effort that seems to have the most impact on the deb files:

• Reduces raw extracted file size by around 670 KB, mostly from icons.icns (453 KB) and to a lesser extent icon.ico (77 KB) and to an even lesser extent the larger syncplay.png files.
• Does not alter size of Syncplay-1.7.4-Setup.exe, which remains 19.5 MB
• Shrinks Syncplay_1.7.4_Portable from 27 MB to 26.9 MB
• Shrinks both syncplay-server.deb and syncplay.deb from 1.5 MB to 1.08 MB

I have three questions:

1. Other than file size, is the re-encoding expected to have any positive and/or negative impact on performance?
2. What platforms (and Python version if relevant) have you tested to ensure that these changes don't cause any compatibility issues?
3. What commands or procedure would I need to follow if I wished to reproduce this work for new graphics? For example, which command line arguments did you use and did you use a tool to automate the process?

The optimizations shouldn't have any negative performance impacts. And, due to lower file size it should load faster on any system but may not be noticeable, it can potentially reduce memory usage for any image where the color palette is able to be reduced.

The PNG optimizations are lossless and within the format specifications so they should be compatible with any standard usage on any OS. Only incompatibilities I expect would be if for some reason there's a specific requirement for an image's palette order or bit depth to remain unchanged.

I've tested on both MacOS and Windows 11, both seem to work fine but I wasn't extensive. Windows XP and older will not work with PNG ICO files. If you find any issues on Linux systems I would be interested in testing different methods for compatibility.

Thanks for the additional information. Syncplay does not officially support operating systems that have reached End of Life status from their developers (for a variety of practical reasons) and so a lack of Windows XP support is not an issue because even the extended support ended back in 2014.

3. What commands or procedure would I need to follow if I wished to reproduce this work for new graphics? For example, which command line arguments did you use and did you use a tool to automate the process?

I use a collection of programs to get better compression, I'll try to list them all out later but you can get good results using a program called FileOptimizer or running ZopfliPNG and/or OxiPNG.

3. What commands or procedure would I need to follow if I wished to reproduce this work for new graphics? For example, which command line arguments did you use and did you use a tool to automate the process?

I use a collection of programs to get better compression

Many of these programs are windows only, closed source, and for some, the creators have disappeared or passed away.

My set:
PNGOut
OxiPNG
ZopfliPNG
ECT
deft4j
DeflOpt

FileOptimizer has most of the ones I use plus more, I usually run it before my own:

PngOptimizer
TruePNG
Leanify
pngwolf
pngrewrite
advpng
pingo
defluff

Thanks for that additional clarification. Merging now to save some space!