iphone: coding a data compression or zipping agent?

I'm creating a simple service for uploading photographs from an iphone to a web server.

However, before the requests is sent, I want the app to compress the pictures (custom format or otherwise) in the ba开发者_运维知识库ckground before sending it.

Any pointers on how I could go about doing this?

Check out the NSDataCategory posted to CocoaDev. It does exactly what you're looking to do.

http://www.cocoadev.com/index.pl?NSDataCategory

I use ziparchive to unzip content downloaded from a server. It also has functionality to create zip files on an iOS device and might be what you are looking for.

http://code.google.com/p/ziparchive/