How to split a wallpaper for multiple monitors on GNU/Linux

So I wanted to split a 3840×1080 wallpaper in two halves for my dual monitor based KDE 4.10.5 setup. Obviously there are several applications that would do the job, but why bother when ImageMagick can do it with a one-liner. The “magick” is achieved by using a geometry argument:

Converting PCD (Kodak Photo CD) files on a Linux system

Back in the old west before the dawn of digital cameras, you could get your photos transferred to a  Kodak Photo CD for everlasting storage. Like other proprietary formats, PCD lost out to the next generation and left those who believed in it behind.