When I started writing katriawm[1], I needed to choose an image format
  to store the window decorations. It needed  to  be  simple  because  I
  didn't  want  to  get my hands dirty with libpng or other libraries. I
  ended up choosing PPM.

  This weekend, I reworked the code a little bit and katriawm  now  uses
  farbfeld[2], which I was already using in infofeld[3].

  I did indeed consider using farbfeld right from the start, but -- if I
  remember correctly -- it was still in some kind  of  flux  back  then.
  Today,  the situation is different. "Version 2" has been released some
  time ago, there is a stable set of conversion tools, there is an imlib
  loader  for  farbfeld  (which  means you can view farbfeld images with
  many tools like feh or sxiv), and there even is a GIMP plugin.

  Farbfeld is a really nice format. It's as simple as it can get.

  Initially, I didn't like that values were stored as big endian,  while
  all  common  Intel  CPUs are little endian. But I get that you have to
  agree  on  something,  so  why  not  use  something   that's   already
  established  in  other  areas?  Big endian is "the network byte order"
  which means that you can use functions like "ntohl()" to convert  from
  big  endian  to  whatever your machine uses. In other words, use those
  functions and never care about endianness again! That's actually  very
  nice.

  ____________________

  1. https://github.com/vain/katriawm

  2. http://tools.suckless.org/farbfeld/

  3. https://github.com/vain/infofeld