Hello
effectively, in category,
- display next to thumbnails a download link, pointing not to the thumbnail but to the original image
- and also setting headers to download the image ?
The usual case is to protect the original images
- you can do this, if your image/gallery field is in DB mode, then you can create a file field and add to it all the images used by image-gallery field of current item
we can add option in v3 to allow download of original, it should be easy but it was not common, and was not added
