Family diagrams saved in he GEDCOM format (*.ged) can be actually saved as plain pictures like the JPGs, or PNGs in tools that support it. One of such programs is yEd which is available for all platforms.
Convert GEDCOM family history file to JPEG bitmap image format.
We found 3 software records in the database related to .ged to .jpg file format conversion.
Microsoft Windows software - convert ged to jpg on Windows
A utility for creating of high quality diagrams
Convert from ged file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned ged to jpg. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Apple macOS / Mac OS X software - convert ged to jpg on OS X
A diagraming tool for OS X
Linux/Unix software - convert ged to jpg on Linux
A Linux version of diagraming tool