[TYPO3] Extension TCA fields... uploading images and resizing them?

[Andrew Plank]

Hi,

I've written an extension that allows users to upload images. I would 
like to be able to resize these images - as they are uploaded - to a 
pre-determined size.

I've read in the docs that once a file exists in the uploads folder, it 
shouldn't be touched in any way, except by Typo3's own internal 
processing. Therefore - I thought - the image needs to be processed 
somewhere between the file beginning its upload, and being finally saved 
into the uploads folder.

Reading further into the docs, I found the "user" type, where the form 
field can be a custom field. However, after a little while tinkering 
with this, I realised that this is only the method to display a custom 
field on the page... It's not how to grab the file as it is uploaded.

Is there some sort of hook into the system one can make that allows one 
to process uploaded images before they are saved?

I find it quite simply boggling that the resizing of uploaded images 
isn't a default feature within the "files" field type when "images" is 
chosen as the allowed file types.

Any help or pointers on this subject would be most greatly appreciated.

//Plankmeister.