prename 's!-!_!g' *.jpg

prename 's!-!_!g; ++$c; s!_[0-9_]+(.[^/.]*)$!_$c$1!' *.jpg

prename 'BEGIN {$c = 1;} s!-!_!g; s!_[0-9_]+(.[^/.]*)$!_$c$1!; ++$c;' *.jpg

find -type d -exec sh -c 'cd "$1" && prename "$0" *.jpg' 's!-!_!g; ++$c; s!_[0-9_]+(.[^/.]*)$!_$c$1!' {} ;