Using background for a poster using Xebaposter shows an empty space on the left margin as shown in figure1, this quetion is based on this anwer.
\def\pgfsysdriver{pgfsys-dvipdfm.def}
\RequirePackage[cmyk]{xcolor}
\RequirePackage{pgf-cmykshadings}
\documentclass[a0paper,landscape,persian]{xebaposter}
\usepackage{ptext}
\usepackage{xepersian}
\settextfont{Yas}
\definecolor{reddishyellow}{cmyk}{0,0.22,1.0,0.0}
\definecolor{lightblue}{cmyk}{0.68,0.25,0.0,0.0}
%\definecolor{lightblue}{rgb}{0.145,0.6666,1}
\begin{document}
\begin{poster}{
borderColor=reddishyellow,
headerColorOne=black,
headerColorTwo=lightblue,
headerborder=closed,
headershape=roundedleft,
headerfont=\Large,
background=shadetb,%user,%plain,none ,shadetb,
%background=none
}{}{}{}
\begin{posterbox}{جداسازی}
\ptext[6]
\end{posterbox}
\end{poster}
\end{document}
The answer to this issue lead to another issue witch is the text exceeds the left margins if i add the options [column=0,span=4,row=0]:
\def\pgfsysdriver{pgfsys-dvipdfm.def}
\RequirePackage[cmyk]{xcolor}
\RequirePackage{pgf-cmykshadings}
\documentclass[margin=0cm,a0paper,landscape,persian]{xebaposter} % <- added margin
\usepackage{ptext}
\usepackage{xepersian}
\settextfont{XB Yas}
\setlength{\parindent}{0pt} % <- added 0pt \parindent
\definecolor{reddishyellow}{cmyk}{0,0.22,1.0,0.0}
\definecolor{lightblue}{cmyk}{0.68,0.25,0.0,0.0}
%\definecolor{lightblue}{rgb}{0.145,0.6666,1}
\begin{document}
\vspace*{-1\baselineskip} % <- added negative baselineskip
\begin{poster}{
borderColor=reddishyellow,
headerColorOne=black,
headerColorTwo=lightblue,
headerborder=closed,
headershape=roundedleft,
headerfont=\Large,
background=shadetb,%user,%plain,none ,shadetb,
%background=none
}{}{}{}
\begin{posterbox}[column=0,span=4,row=0]{جداسازی}
\ptext[6]
\end{posterbox}
\end{poster}
\end{document}


