How can I achieve the maximum zip compression?

Question

I would like to make a "standard" zip file which contain .jpg images. Which software and switches / options should I use to achieve the maximum compression ratio? I mean maybe I can make a solid archive with some special compression options and high memory usage with 7zip.

Solution

As jpeg files are already compressed, you could tell zip to just store the files without trying to compress them at all. The switch --compression-method store (or -Z store or -0) will do that. But don't expect to gain anything: usually zip is smart enough to detect that compression won't help.

Comments

[ChrisInEdmonton]

jpegs are typically highly compressed with lossy compression already. You almost certainly can't get any significant additional compression with any lossless compression algorithms.

[Konstantin]

Yes, I know, but I am curious which switches and options can I use. For example -mx=9 -mpass=15 etc. Mabye even more exist.

[ChrisInEdmonton]

On jpegs? No switches will prove generally useful.

[Daniel R Hicks]

Undestand that when you attempt to compress an already well-compressed file the "compressed" image is actually larger than the original. A fellow named Shannon made that the law, and everyone's been afraid to break it since.