我想要执行以下操作：
\documentclass[pstricks]{standalone}
\psset{unit=1in}
\begin{document}
\begin{pspicture}(2in, 1in)
\psframe[linecolor=red, fillcolor=red, fillstyle=solid, dimen=outer](0, 0)(1, 1)
\psframe[linecolor=black, fillcolor=black, fillstyle=solid, dimen=outer](1, 0)(2, 1)
\end{pspicture}
\end{document}
并得到了我想要的如下：
但是，出于某种原因，我想要一个黑色方块的外部图像。好吧，这是我为黑色方块图像创建的：
\documentclass[pstricks]{standalone}
\psset{unit=1in}
\begin{document}
\begin{pspicture}(1in, 1in)
\psframe[linecolor=black, fillcolor=black, fillstyle=solid, dimen=outer](0, 0)(1, 1)
\end{pspicture}
\end{document}
将其另存为blacksquare.pdf。然后，当我执行以下操作时：
\documentclass[pstricks]{standalone}
\psset{unit=1in}
\usepackage{graphicx}
\begin{document}
\begin{pspicture}(2in, 1in)
\psframe[linecolor=red, fillcolor=red, fillstyle=solid, dimen=outer](0, 0)(1, 1)
\rput[lb](1,0){\includegraphics{blacksquare}}
\end{pspicture}
\end{document}
结果是：
中间有一条细细的白线。这条边距是从哪里来的？我该如何将其去除？
按要求提供的文件清单：
*File List*
standalone.cls 2012/09/15 v1.1b Class to compile TeX sub-files standalone
ifluatex.sty 2010/03/01 v1.3 Provides the ifluatex switch (HO)
ifpdf.sty 2011/01/30 v2.3 Provides the ifpdf switch (HO)
ifxetex.sty 2010/09/12 v0.6 Provides ifxetex conditional
xkeyval.sty 2014/12/03 v2.7a package option processing (HA)
xkeyval.tex 2014/12/03 v2.7a key=value parser (HA)
standalone.cfg 2012/09/15 v1.1b Default configuration file for 'standalone'
class
article.cls 2014/09/29 v1.4h Standard LaTeX document class
size10.clo 2014/09/29 v1.4h Standard LaTeX file (size option)
pstricks.sty 2013/12/12 v0.60 LaTeX wrapper for `PSTricks' (RN,HV)
pstricks.tex 2014/10/25 v2.60 `PSTricks' (tvz,hv)
pst-xkey.tex 2005/11/25 v1.6 PSTricks specialization of xkeyval (HA)
pst-fp.tex 2014/10/25 v2.60 `PST-fp' (hv)
xcolor.sty 2007/01/21 v2.11 LaTeX color extensions (UK)
color.cfg 2007/01/18 v1.5 color configuration of teTeX/TeXLive
xetex.def 2015/03/25 v4.04 LaTeX color/graphics driver for XeTeX (TeX Liv
e/RRM/JK)
graphicx.sty 2014/10/28 v1.0g Enhanced LaTeX Graphics (DPC,SPQR)
graphics.sty 2014/10/28 v1.0p Standard LaTeX Graphics (DPC,SPQR)
trig.sty 1999/03/16 v1.09 sin cos tan (DPC)
graphics.cfg 2010/04/23 v1.9 graphics configuration of TeX Live
blacksquare.pdf Graphic file (type QTm)
***********