“There are many tools for Linux which can be used to transform
or manipulate images in particular ways. One of the most
versatile of these is the ImageMagick suite of imaging
tools (available in the Debian imagemagick package…).”
“One of these ImageMagick tools, mogrify, is particularly
useful for performing fast command-line image transforms — use it
to scale the size of images, rotate images, and reduce colors in an
image. It always takes the name of the file to work on as an
argument, and it writes its changes to that file. Use a hyphen, -,
to specify the standard input, in which case it writes its output
to the standard output.”
“Let’s take the sample image at the right and put it through the
works. What can we do to it from the command line?”