How to resize automatically when users upload images by CCK image field I would like to make the size of images smaller automatically when users upload them using CCK image field.

For example, I would like to let users upload big sized images like 5MB but resize them smaller automatically like 0.5MB before saved on the server.

The reason is that the capacity I can use on the shared server is very limited. Of course I can set "Maximum upload size per file" to a small size but then users who have big sized images but don't know how to resize them before upload will not be able to upload them. I have tried also "image cache" a bit but it doesn't seem to save the files with the name, attributes and in the directory specified by CCK image field.  

I don't know if this kind of thing is possible to achieve or not.. Any Idea?
Imagecache is great, but since it keeps the original file around, it won't save space. In fact, if you have multiple presets, it will increase your disk usage as it creates its caches of images of those sizes.

What you may want to investigate is putting some logic into nodeapi() (or, if on Drupal7, its equivalent function) when saving your node that looks at the filepath of whatever image field you are concerned with and does some image manipulation on it if it is over a certain size and then saving it in place.