What parameter is available to remove the thin border around \ncput*?

What parameter is available to remove the thin border around \ncput*?

The objective is to make the background color of the box containing the label transparent.
\documentclass[pstricks]{standalone}
\usepackage{pst-eucl}

\begin{document}
\begin{pspicture}[showgrid=false](4,4)
    \pstGeonode[PosAngle={90}]
        (1,1){A}
        (3,3){B}
    \ncarc[arcangle=-30,linestyle=dashed,linecolor=gray]{A}{B}
  \ncput*[nrot=:0]{$2\sqrt2$}  
\end{pspicture}
\end{document}
I use -transparent white when invoking ImageMagick's convert. Unfortunately there is still a thin yet visible border around the box as follows. Is there any option to remove such an unwanted border?

This question is my attempt to solve my other question here.