use gcf as default figure handle, if not provided as input
use gcf as default figure handle, if not provided as input

qqyoungqq/export_fig,altmany/export_fig,dcherian/export_fig,JacobD10/export_fig,altmany/export_fig,hyiltiz/export_fig,hyiltiz/export_fig,JacobD10/export_fig,dcherian/export_fig