XnView Software

I need to save a jpg file (a map) as bi-level blackandwhite file. As I understand the XNview website this should be possible; the extension will be jbg or bie or jbig. But when I want to save my file in that format there is no such joice. In the options, I have already activated "all formats".
Can anybody help me with this (I am a beginner in this type of question)? Vous pouves repondre en francais aussi.

Jbg is a completely different format from jpg, if you need a bi-level jpg file, don't use jbg.

As for saving in the jbg format, the extension in xnview is "JBG". Keep in mind that xnview has commonly used filetypes at the top of the list. Have you looked ofr jbig at both the very top of the list when you're saving & lower in the list?