One of my major projects right now is to try to losslessly compress the highest-visibility PNG files I can find. This helps articles load faster and cuts server costs.
After some experimentation, I've found that the best chain of programs (linked in a small bash script) to achieve maximum compression is:
- PNGOUT (very nice zlib implementation and custom DEFLATE algorithm; best compression ratio at the cost of CPU)
- advpng -z4 (maximum AdvanceCOMP restructuring)
- advdef -z4 (maximum AdvanceCOMP compression, using 7zip)
- OptiPNG (sometimes catches a few extra bytes after the above)
- DeflOpt (fast, and almost always catches a handful of bytes on small images, sometimes kilobytes-worth on larger ones)
I haven't come up with a notation for listing my compression process like Tene has; usually I just manually list what I've done with a file. Where appropriate, sometimes I'll index an image's color and truncate its palette to save even more space, but generally I stick to pure lossless methods.
As of 1/2009, the Wikipedia logo itself was actually last compressed on my computer, using this method.
By the way, I'm still waiting to hear back from Ben Jos Walbeehm regarding his GCC-compiled binary of DeflOpt. If you happen to have access to the Linux executable, please leave me a message. Wine is great, but it's definitely slower than native code.
Update: An anonymous contributor was kind enough to provide me with the link! The elusive Linux version can be found here.
