Appending 2 images of different sizes?

[magick]

To append images of difference sizes, use the montage program with a mode of concatenation (e.g. -mode concatentate).

[anthony]

IM montage concatinate does not center align images. Though you can
do it without resorting to concatenate mode.
EG vertical append centered
montage images... -geometry '1x1+0+0<' -tile 1x output.png

I have noted this in IM examples at
http://www.cit.gu.edu.au/~anthony/graph ... ge/#append
But example results have not been finished.

As an alturnative see appending images in IM examples.
http://www.cit.gu.edu.au/~anthony/graph ... cs/#append
It gives methods of appending with alignment until such time as IM provides justification that is seperate to gravity.