The default viewer for any image in Xubuntu is Ristretto Image Viewer. Using Xubuntu 16.04 LTS, it was possible to read image.ascii.pgm with Ristretto. With 18.04 the program opens but no images are displayed.


  • Is there a way of reading image.ascii.pgm files with the Ristretto Image Viewer in Xubuntu 18.04 LTS?
  • If not, do you suggest to use another viewer instead? If so, how to use another viewer as default?

Temporary workaround: I can read the images using Inkscape, but, as you can imagine, it is not a light-weight viewer program; it is a heavy vector-graphics image editor (like shooting a fly with a cannon).

ASCII PGM (Portable Gray Map) format for 2D grayscale graphics information. More info here.

  • For your first question: There is a bug report on this issue. It seems that it is fixed in the 0.8.4 version.

  • For your second question: I am highly recommending Nomacs image viewer. You can install it by running:

    sudo apt install nomacs

    To set it as default for a specific file type, right-click the file you want to have opened with Nomacs, then Properties...Open With:Nomacs.

  • +1 problem solved – Leos313 Oct 2 at 10:23
  • however, now I really LOVE Nomacs :) – Leos313 Oct 2 at 10:39
  • 1
    @Leos313 Yes, it's an excellent program. I have completely uninstalled Ristretto and just use Nomacs for a few years now. Its latest version, 3.12, is even better (I have tried it in Windows 10 a while ago), however it's not available in the bionic repositories. – user3140225 Oct 2 at 11:24

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