Automatically reduce weight of images

Hi.

I have a community where members can upload images, using (the great!) Node Gallery module.

Now, on the web, you dont need to have «big» images (say 2.5 Mo). Big images slow down their display, «eat up» your server and anyway, computer screen have low resolution (72? 96? dpi).

Another thing: most users upload images regardless of weight since sites like facebook or myspace «crunch down» their images for them.

My question: is it possible to automatically reduce the weight of images on upload, so that users dont have to bother about that? Say that I want to automatically reduce images to 512 Ko when users upload them. Is their a way to do it in Node Gallery? Do I need another module?

In ...admin>content>node-type>node-gallery-image>fields>field_node_gallery_image I have noticed that it is possible to set a maximum image resolution: «If a larger image is uploaded, it will be resized to reflect the given width and height.»

But what about weight? Or is it the same thing? I have to admit that I'm a bit confused with size, weight and resolution.

Thanks for your time.

R.