Curtail UIImage download size from WEB

I have an application that downloads im开发者_开发技巧ages based on URL using the call:

img = [[UIImage alloc] initWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:urlToImage] options:0 error:&err]];

where URL is an image on the WEB.

I really want to curtail the amount of data transfer, so would like to reduce the file size of the download.

I was wondering if anyone has a magic way of reducing the file size of the download short of implementing a PHP server process to be the go between to take care of this.

Thanks in advance!