Creating an industrial-style wallpaper (with GIMP)

“The aim of this step is to get a very nice high contrast
black/white image of the cranes on my photo. We can do that
using:

“- Colors / Components / Channel mixer

“We want to get a white background (which will be easily removed
later), while our cranes on the picture shall be almost dark gray
and black.

“First I checked “Monochrome” in the channel mixer. Next step is
to play around with the red/green/blue channel values so that you
get a walmost white background. The sky shall be white, and because
it is blue in the original image I raise the values of the Blue
channel until it is completely white.”

Complete Story