I need to gzip a image file how do I do that?

to compress or to uncompress?

gunzip <name of the file>

compress

usage: gzip [-cdfhlLnNrtvV19] [-S suffix] [file ...]
-c --stdout write on standard output, keep original files unchanged
-d --decompress decompress
-f --force force overwrite of output file and compress links
-h --help give this help
-l --list list compressed file contents
-L --license display software license
-n --no-name do not save or restore the original name and time stamp
-N --name save or restore the original name and time stamp
-q --quiet suppress all warnings
-r --recursive operate recursively on directories
-S .suf --suffix .suf use suffix .suf on compressed files
-t --test test compressed file integrity
-v --verbose verbose mode
-V --version display version number
-1 --fast compress faster
-9 --best compress better
--rsyncable Make rsync-friendly archive
file... files to (de)compress. If none given, use standard input.

gzip -1 <name of the file>

I think?

What i feel is that you have a file that you need to compress , may be it is a tar file or anything like that , for compressing issue a commnd gzip -9 <filename> .. this option gzips the entire file as a single file with the new name as <filename>.gz .. otherwise if you just want to have the other file intact and subsequently have a compressed one , issue gzip -c <filename> . for unzipping this file issue gunzip <filename> ... ... hope this can help you ..
cheers
Shaheen

Thanks Megaman X and shaheen