Trying to resize a video by cropping the sides and adding height is it possible to do this with ffmpeg? Basically, I want to convert an mp4 file that's in landscape to portrait.  It's a single image on a black background with no sound.  I want to keep the size and aspect ratio of the image intact and my plan is to convert it from 1280x720 to 720x1280.

I'm playing around with crop and padding, but I'm wondering if there's a way to get this done with one command, and if I need to reencode it.
For a target size of 720x1280, you would use

ffmpeg -i img.png -vf scale=-1:1280:flags=lanczos,crop=720:1280:(iw-720)/2:0 out.png