How can I put three pictures with sub-captions in two rows using subfig package?

Question

I would like to put three pictures with sub-captions in two rows using the subfig package. I want to center the single picture in the second row. I use the following code :

\documentclass[12pt,leqno]{book}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc} 
\usepackage{lmodern} 
\usepackage{graphicx}                 
\usepackage{float}
\usepackage{keyval,caption,subfig}
\captionsetup[subfigure]{%format=hang, singlelinecheck=false, font={tt,bf,sc}}
\newsubfloat[position=top,listofformat=subsimple]{figure}

\parindent 1cm
\parskip 0.2cm
\topmargin 0.2cm
\oddsidemargin 1cm
\evensidemargin 0.5cm
\textwidth 15cm
\textheight 21cm

\DeclareGraphicsExtensions{.png}

\begin{document}

\begin{figure}[H]%
\centering
\subfloat[First subtitle]{
\begin{picture}(226,139)
{\includegraphics{abra_1_a}}
\end{picture}
}
\qquad
\subfloat[Second subtitle]{
\begin{picture}(226,139)
{\includegraphics{abra_1_b}}
\end{picture}
}\\
\subfloat[Third subtitle]{
\begin{picture}(226,139)
{\includegraphics{abra_1_c}}
\end{picture}
}%
\caption{Assignment}
\end{figure}

\end{document}    

Result : The pictures appear in three rows.

Question : What is wrong in my code ?

Answer 1

Why do you use the picture environment? The following does what you require:

\documentclass[12pt,leqno]{book}
\usepackage[demo]{graphicx}                 
\usepackage{float}
\usepackage{subfig}

\begin{document}

\begin{figure}[H]%
\centering
\subfloat[First subtitle]{\includegraphics{abra_1_a}}\hfill%
\subfloat[Second subtitle]{\includegraphics{abra_1_b}}\\
\subfloat[Third subtitle]{\includegraphics{abra_1_c}}
\caption{Assignment}
\end{figure}

\end{document}

Using the optional argument of \includegraphics you can change the figure attributes, e.g.,

\includegraphics[width=.3\linewidth]{abra_1_a}

I used the demo option for graphicx to make my example compilable for everyone; do not use that option in your actual document.

Answer 2

There is no need for the picture environment. Use the width option

\documentclass[12pt,leqno]{book}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc} 
\usepackage{lmodern} 
\usepackage[demo]{graphicx}% DELETE [DEMO] after trying
\usepackage{keyval,caption,subfig}
\captionsetup[subfigure]{format=hang, singlelinecheck=false, font={tt,bf,sc}}

\begin{document}
\begin{figure}
\centering
\subfloat[First subtitle]{\includegraphics[width=0.49\textwidth]{abra_1_a}}
\hfill
\subfloat[Second subtitle]{\includegraphics[width=0.49\textwidth]{abra_1_b}}

\subfloat[Third subtitle]{\includegraphics{abra_1_c}}

\caption{Assignment}
\end{figure}

\end{document}