Using cflow

Needed programs

cflow (from gnu)
cflow2dot (from cflow2vcg at sourceforge)
dot (from graphviz)

Create compliant Cflow output

cflow --format=posix --omit-arguments --level-indent='0=\t' --level-indent='1=\t' --level-indent=start='\t' -m "function_name" "source_file" > "out.cf"

Create dot file.

cflow2dot < "out.cf" > "out.dot"

Create image

dot -Tjpg "out.dot" -o "image.jpg"