[gradsusr] Error with sys command

[iri]

Hi GrADS users and developeres !

I create some PNG plots succesfully.
I wish to change the colors palette.
I invoke convert (imagemagik) via the sys command from a script.

convert is installed and work fine directly from a Bash or Python script
from Debian Bulleyes.

cmd = "./convertPNG.sh "%pngFile
say cmd
sys (cmd)

I get this error :

./convertPNG.sh ./img/aromeOM/20211016/00/antilles_uv_cape_rh2m_00.png
convert:
/opt/opengrads/opengrads-2.2.1.oga.1/Linux/Versions/2.2.1.oga.1/x86_64/gex/libstdc++.so.6:
version `CXXABI_1.3.8' not found (required by
/lib/x86_64-linux-gnu/libicuuc.so.67)
Syntax Error
  Error occurred on line 1
  In file ./img/aromeOM/20211016/00/antilles_uv_cape_rh2m_00.png


I tried this :

'!./convertPNG.sh '%pngFile

I get this similar error :

convert:
/opt/opengrads/opengrads-2.2.1.oga.1/Linux/Versions/2.2.1.oga.1/x86_64/gex/libstdc++.so.6:
version `CXXABI_1.3.8' not found (required by
/lib/x86_64-linux-gnu/libicuuc.so.67)


convertPNG.sh :

if [ -f "$1" ]; then
 convert -type palette -colors 255 "$1" png8:"$1"
fi
exit 0

Is it only the available version of libstdc++ that is at issue?

Any help is appreciated to solve it,
steph