I created this by running
jbig2 -i Tests/LibGfx/test-inputs/bmp/bitmap -f bmp -o bitmap -F jb2
using the `jbig2` tool whose source code is in the zip file here:
https://www.itu.int/rec/T-REC-T.88-201808-I
(Just `make jbig2` in Software/JBIG2_SampleSoftware-A20180829/source
was enough to build it.)
As far as I can tell (cf `JBIG2_EncMain()` which always writes `1`
to the flags byte in the file header), this tool always writes files
in the sequential organization.
