Output elements missing for QCD marker

[bitsgalore]

Command:

  python3 ~/jpylyzer/cli.py --recurse ~/jpylyzer-test-files/ > jpylyzer.xml
  xmllint --noout --schema ~/jpylyzer/xsd/jpylyzer-v-2-0.xsd  jpylyzer.xml

Result:

jpylyzer.xml:3404: element qcd: Schemas validity error : Element '{http://openpreservation.org/ns/jpylyzer/v2/}qcd': Missing child element(s). Expected is one of ( {http://openpreservation.org/ns/jpylyzer/v2/}mu, {http://openpreservation.org/ns/jpylyzer/v2/}epsilon ).
jpylyzer.xml:17090: element qcd: Schemas validity error : Element '{http://openpreservation.org/ns/jpylyzer/v2/}qcd': Missing child element(s). Expected is one of ( {http://openpreservation.org/ns/jpylyzer/v2/}mu, {http://openpreservation.org/ns/jpylyzer/v2/}epsilon ).
jpylyzer.xml fails to validate

Turns out for some images the qcd element doesn't contain mu or epsilon child elements.

[bitsgalore]

Affects following files:

is_jpx.jp2

            <qcd>
                <lqcd>4</lqcd>
                <qStyle>no quantization</qStyle>
                <guardBits>2</guardBits>
            </qcd>

oj-tileindex-error-2.jp2

            <qcd>
                <lqcd>4</lqcd>
                <qStyle>no quantization</qStyle>
                <guardBits>2</guardBits>
            </qcd>

[bitsgalore]

Happens if levels equals 0. Fixed by https://github.com/openpreserve/jpylyzer/commit/733f16d0d2db53ff1480557f908ed9c3d9ca1db1.