increase canvas size without increasing layer size?

[erinspice]

Hi! I need to resize an image by adding a strip of white underneath the image I've read in. I've consulted the API, but I can't seem to find anything that will do this. Do you guys know of a way to do this? I've found a couple of workarounds (composite over white image the desired size, border and crop), but I wish there were something more direct.

[anthony]

Look at Splice