Feature request: Scroll all images up/down in a slideshow

[martin-niklasson]

I use feh on a Raspberry pi as a digital photo frame. It's great! It displays images from several different cameras with slightly different aspect ratios and displays them on a Full HD 16:9 screen. The relevant options I use are: --full-screen --zoom fill --quiet --hide-pointer --slideshow-delay 5 However, many of my photos are of peoples faces, and since this centers the images, it quite frequently cuts off their eyes!

I wish for a feature where I can tell it to show:

          this              instead of this
 .....................   .....................
 .                   .   .                   .
 .+-----------------+.   .                   .
 .|                 |.   .+-----------------+.
 .|                 |.   .|                 |.
 .|                 |.   .|                 |.
 .|                 |.   .|                 |.
 .+-----------------+.   .|                 |.
 .                   .   .+-----------------+.
 .                   .   .                   .
 .                   .   .                   .
 .....................   .....................

I hope that makes sense.

I imagine just a single command line option applied to all pictures, where I can tell the percentage of scroll up/down. Maybe something like: feh -ypos 0 (scroll all the way to the top) feh -ypos 100 (scroll all the way to the bottom) and 50 being the current default. For symmetry, I guess there should be a similar option for X direction, even though I can't see that I would need it.

I can volunteer to help with implementation, if this is something that would be useful.