There is a workshop where stundents must submit (big) .jpg files. How to force download, not show pictures in browser?
Tried to look from Site administration > Plugins > Activity modules > File with no help.
I am afraid that is not supported at the moment. The only workaround coming to my mind is to ask students to submit the JPEG archived in a ZIP file. I know, it has no sense from the any perspective (compression etc) and is just an extra workload for both students and reviewers...
It might be solvable via a new setting "Automatically embed attached images". At the moment, Workshop automatically embeds them (like Forum does). If you think it might be useful for others too, please report it as a new feature request.
The alternative solution (which I would actually prefer) is a general in-core (ie not Workshop specific) feature that big images would be automatically scaled to a preview-sized version like eg MediaWiki does. Such a feature might be useful for other places dealing with images (Forum, Assignment). Chances are it is already reported.