[magick-users] Using identify for unique IDs

[duc.sequere.aut.de.via.decede at imagemagick.org]

> how does this process multi-frame images or movies?  does it iterate
> over every pixel in every frame?

You can also add '[0]' to your filename to limit the signature to the
first frame only:

  identify -format '%#' 'mymovie.gif[0]'