(Ted Harding) wrote:
Have a look at 'montage' (part of the InageMagick package). While it is usually used for making a true montage out of several separate images, there is nothing to stop you using it for just one.
Thanks, because this lead me to the option I needed in convert!
What I need is really simple: convert -resize 350x350 -extent 350x350 -gravity center old.png new.png