Despite being old as the hills and seemingly unchanged over the years ImageMagick still manages to be slow. It is a mystery how the developers managed this feat.
It's a shame that netpbm seems to be mostly dead, it always worked much better for the kind of tasks that most people use ImageMagick for, at least for me.
OTOH, when using screen, it completely poops itself. Sadface.
Also, wow, it's slow.