# algorithm2e and color

I am trying to color the background of the caption in algorithm (using algorithm2e).

I have modified the original command as follow directly in the .sty file.

However, as you can see on the image, the result is not convenient. I would like the whole "row" to be in gray (I put row into brackets as it is not a tabular).

\newcommand{\algocf@makecaption@ruled}[2]{%
\global\sbox\algocf@capbox{\hskip\AlCapHSkip![enter image description here][2]
\parbox[t]{\hsize}{\colorbox{gray!50}{\algocf@captiontext{#1}{#2}}}}
}%


The original :

\newcommand{\algocf@makecaption@ruled}[2]{%
\global\sbox\algocf@capbox{\hskip\AlCapHSkip% .5\algomargin%
\parbox[t]{\hsize}{\algocf@captiontext{#1}{#2}}}
}%


The complete code :

\documentclass{article}
\usepackage{etex}
\usepackage{easybmat}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{xcolor}
\usepackage{algorithm2e}
\RestyleAlgo{algoruled}

\begin{document}

\SetKw{KwFrom}{from}

\newenvironment{algo}{
\begin{algorithm}[H]
\DontPrintSemicolon \SetAlgoVlined}
{\end{algorithm}}

\begin{algo}\label{algotrigsup}
\caption{Caption of the algo}
\For{$k$ \KwFrom $n-1$ \KwTo $1$}{
$x_k=b_k$\;
\For{$j$ \KwFrom $k+1$ \KwTo $n$}{
$x_k=x_k -a_{kj} x_j$\;
}
$x_k=\displaystyle \frac{x_k}{a_{kk}}$
}
\end{algo}

\end{document}

• Please, do not make any modifications directly in standard .sty files. – Gonzalo Medina May 8 '14 at 14:05
• So how can I modify a package ? I mean generally speaking, for any package – hindi May 8 '14 at 14:07
• If the change is local to just one document, you can make the change in the .tex file as I did in my answer. If you really need to change a package, then make a copy of the original .sty file, save it with a different name and make the changes in the renamed file; of course, now you load the renamed package, not the original. – Gonzalo Medina May 8 '14 at 14:09

Here's one possibility (the \parbox has to be inside the \colorbox and some vertical and horizontal spacing adjustments are required):

\documentclass{article}
\usepackage[ruled]{algorithm2e}
\usepackage{xcolor}

\colorlet{AlgCaptionColor}{gray!30}

\makeatletter
\renewcommand{\algocf@makecaption@ruled}[2]{%
\global\sbox\algocf@capbox{\colorbox{AlgCaptionColor}{\hskip\AlCapHSkip% .5\algomargin%
\parbox[t]{\hsize}{\algocf@captiontext{\strut#1}{\strut#2\strut}}\hskip.6\algomargin}}% then caption is not centered
}%
\setlength{\interspacetitleruled}{0pt}%
\makeatother

\begin{document}

\begin{algorithm}[H]
\SetAlgoLined
\KwData{this text}
\KwResult{how to write algorithm with \LaTeX2e }
initialization\;
\While{not at end of this document}{