In /usr/bin/grap2graph line 70:
if ! tmp=`(umask 077 && mktemp -d -q "$d/grap2graph-XXXXXX") 2> /dev/null`
         ^-- SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
if ! tmp=$((umask 077 && mktemp -d -q "$d/grap2graph-XXXXXX") 2> /dev/null)


In /usr/bin/grap2graph line 89:
is_convert_recent=`convert -help | grep -e -trim`
                  ^-----------------------------^ SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
is_convert_recent=$(convert -help | grep -e -trim)


In /usr/bin/grap2graph line 93:
    convert_trim_arg="-crop 0x0"
    ^--------------^ SC2034: convert_trim_arg appears unused. Verify use (or export if used externally).


In /usr/bin/grap2graph line 96:
trap 'exit_status=$?; rm -rf "$tmp" && exit $exit_status' EXIT INT TERM
     ^-- SC2154: exit_status is referenced but not assigned.


In /usr/bin/grap2graph line 104:
    convert -trim $convert_opts - "$tmp"/grap2graph.$format \
                  ^-----------^ SC2086: Double quote to prevent globbing and word splitting.
                                                    ^-----^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
    convert -trim "$convert_opts" - "$tmp"/grap2graph."$format" \


In /usr/bin/grap2graph line 105:
    && cat "$tmp"/grap2graph.$format
                             ^-----^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
    && cat "$tmp"/grap2graph."$format"

For more information:
  https://www.shellcheck.net/wiki/SC2034 -- convert_trim_arg appears unused. ...
  https://www.shellcheck.net/wiki/SC2154 -- exit_status is referenced but not...
  https://www.shellcheck.net/wiki/SC2086 -- Double quote to prevent globbing ...