[Dvipng] Breaks in brackets

[Kevin D. Smith]

I am running the following code in latex then using dvipng 1.9 to  
generate an image.  You'll see in the attached image that there are  
breaks in the first four brackets.  I've tried various quality levels  
as well as different DPIs, but I just can't get them to go away.  Do  
you have any suggestions?

\documentclass{article} \renewcommand{\rmdefault }{ptm} \usepackage 
{mtpro2} \makea
tletter
address@hidden 
\break\plasTeXre
address@hidden
address@hidden 
\ifhmode\hrule\e
lse\vrule\fi height 2pt depth 0pt width 2pt\hskip2pt}}{}
\begin{document}

\begin{plasTeXimage}{images/img-0001.png}
\[  \left[ \begin{array}{r} w \\ x \\ y \\ z \\ \end{array}\right] =  
\left[ \begin
{array}{rrr} 1 &  1 &  1 \\ 1 &  1 &  -1 \\ 1 &  -1 &  1 \\ 1 &  -1  
&  -1 \end{arr
ay}\right] \left[ \begin{array}{c} \beta _0\\ \beta _1\\ \beta _2 \end 
{array}\righ
t]  \]
\end{plasTeXimage}

\end{document}\endinput

Kevin D. Smith
address@hidden