Missing region in PDF

[hackerb9]

I have a particular PNG file which I am embedding in a PDF as a JBIG2 stream. However, horizontal and vertical lines are missing from one section in the middle.

$ jbig2 -s -a -p -v schem1.png 
Processing "schem1.png"...
source image: 14816 x 9600 (1 bits) 72dpi x 72dpi, refcount = 1
thresholded image: 14816 x 9600 (1 bits) 72dpi x 72dpi, refcount = 2

$ jbig2topdf.py output >output.pdf

$ convert output.pdf -colorspace gray -depth 1 broken.png

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I have tried various PDF viewers plus web browsers and ImageMagick, and the problem is always the same. My guess is it is a bug in the PDF section of the jbig2enc code as normal JBIG2 output looks fine:

$ jbig2 schem1.png | jbig2dec /dev/stdin -o works.png

[zdenop]

This this:
jbig2 -p -v schem1.png > schem1.jb2 && python jbig2topdf.py -s schem1.jb2 > out.pdf

This command avoids symbol mode (-s) and uses generic region encoding, which is more reliable for images that
are not text-based, like your schematic drawing.