It is sad but true: More than two years later in netpbm (2:10.0-15.3) of Ubuntu 16.04.1 LTS the bug is still not fixed :-(
Fortunately, there is another tool set (ImageMagick) which has a working conversion tool (convert). So one can convert xwd output to file.png by executing:
xwd -root -display :0 | convert xwd:- file.png
I attached file "test.xwd" which shows the bug of xwdtopnm
It is sad but true: More than two years later in netpbm (2:10.0-15.3) of Ubuntu 16.04.1 LTS the bug is still not fixed :-(
Fortunately, there is another tool set (ImageMagick) which has a working conversion tool (convert). So one can convert xwd output to file.png by executing:
xwd -root -display :0 | convert xwd:- file.png
I attached file "test.xwd" which shows the bug of xwdtopnm