How is the compression ratio set when creating archives in File Roller? If an archive of JPEG images is compressed, can it be un-compressed so all the color information of the original image is intact?

I have occasion to send sets of image files, usually JPEG format, to Windows users. They have the native ability to manipulate ".zip" archives, so that is my preferred archive format. However, File Roller's default compression ratio when creating ".zip" archives is 1:1 and I can't figure out how to increase it. At that rate, I may as well just attach individual photos to e-mails, or, in the case of a set of many images (often the case), go through the hassle and expense of burning the images to a CD and send them by surface mail.

I don't want to compress or reduce the resolution of the JPEG's-- I want my correspondents to receive high-resolution images with the broadest color-range possible, best-suited for printing. Otherwise, I could just optimize the JPEG's for web publication and upload them to my MySpace photo album. But that isn't the best quality for printing, which usually is my goal.

Any help increasing the compression ratio in ".zip" format with File Roller would be appreciated, and any advice as to whether all the JPEG color information can be recovered when the archive is un-compressed, would be appreciated. By the way, this is version #2.22.4 of File Roller.

Many thanks and best regards to all.

first when you " zip, bz2, gz,... " a folder There is NO DATA LOST so this -
so this question is mute and dose not apply and ( the statement is a false one )
zip dose not work that way
you can NOT "increase it"
the jpg's are already compressed so the zip file is just a container , so there is no further compression on them when you zip them .
this is imposable, a zip archive will not recompress a already compressed jpg

Personally i think jpg's should be illegal seeing as they are " lossy compression " in that a photo editor MUST through out image data in order to save to a jpg

i use png's they are "lossless compression " ( uses zlib)

File-roller itself is very easy - it doesn't make any attempt to provide sophisticated settings. As a front-end to common system tools (like tar and gzip) it will simply use the default settings for those tools.

Using common compression tools on JPEG images will not really bother with colors and quality - it will simply try to compress the file as any other binary file. So the JPEG file will be exactly the same after un-compressing. Archiving tools are not supposed to allow data-loss. JPEG files are usually quite well compressed on their own, so compression tools usually can not yield spectacularly small sizes (unlike TIFF files, which can be compress greatly sometimes, depending on tag contents).

Linux Archive

Thanks, everyone, for clarifying my basic misconceptions about the nature of JPEG and compression. Now I "get it".