what we need is a way to limit the maximum dimension of an image posted within the img tags.
perfect would be if it matched the screen-size.

Auto resizing of images in posts, etc by CSS.

With this CSS added to the end of your index.css file, you can disable all SMF admin resize settings for images and avatars. This CSS will even resize images correctly for phones, if your theme is built to handle them, regardless of the size of the image.

Re: Auto resizing of images in posts, etc by CSS.

It is a pretty easy thing to add or remove. The best part is that you don't have to add any of the code in between other code or in the middle of a template- it's just adding it to the very bottom of your index.css. Like Antechinus said; if you don't like the results, just go back into that file and remove it.

Is it worth trying?

Linkback: https://fractalforums.org/discuss-fractalforums/5/just-saying-auto-resizing-of-images-in-posts-etc-by-css/319/

Finally!!
The issue was solved withthe help of 3dickulus!

Now, if you click on an image in a thread generated by upload of an image to the gallery, like this:
https://fractalforums.org/fractal-image-gallery/18/biocell/1003/msg5245#new
it opens the image in full view, downsized to your screen resolution. If you click again, it will zoom into full resolution, towards the point where you clicked.

Thanks 3dickulus!!