Padd icons with empty space using linux convert utility

Question

I have a bunch of PNG icons with different sizes:

96x96
96x23
96x46
96x80
etc...

How can I, with the help of linux convert utility, padd them. So that all of the icons get the same square dimensions, say 96x96.

The existing image should be centered. Like this (for the image of the size 5x5):

.....
xxxxx
xxxxx
xxxxx
.....

I used the following command to scale the image. Maybe, I just forgot some parameter?

convert -size 96x96 icon.png -resize 96x96 +profile '*' scaled.png

Answer 1

This one should help:

convert             \
   icon.png         \
  -scale 96x96      \
  -background white \
  -gravity center   \
  -extent 96x96     \
  +profile '*'      \
   scaled.png