Bill Hill wrote:
convert -border 2x0 -bordercolor #0000FF -resize 350x350 input.jpg -background #FFE000 -gravity center -extent 350x350 output.jpg
That's just what I needed, thanks (I got there on most of it, but there's some extras in there I didn't know).
Any idea how to go for transparent backgrounds? (Aside from not using .jpg, of-course!)