Let's say we have a bunch of images with varying dimensions (w×h) and I want them all to fit into a 16:9 canvas, but I don't want to define a fixed size (like 1920×1080px). The wider side should stay the same, only the narrow side of the image should be padded with a given color or transparency until the desired aspect ration is met.
It seem like there's currently no way to achieve that, so I'm asking for a solution.
Related: https://newsgroup.xnview.com/viewtopic.php?f=79&t=38104
Basically what this script does: http://www.fmwconcepts.com/imagemagick/aspectpad/