\documentclass[convert]{standalone} ignores linebreak

Question

I tried to combine this answer Compile a LaTeX document into a PNG image that's as short as possible with my answer Add column in a table

But the pdflatex -shell-escape table.tex ignores linebreaks and the 3 tables are horizontally aligned and not vertically.

table.tex

\documentclass[convert]{standalone}
% \documentclass{article}

\usepackage{booktabs} % for nice lines
\usepackage{siunitx}  % nice numbers and units and 'S' in table
\usepackage{multirow} % enable \multirow command

\begin{document}
short answer to your question:\\
\begin{tabular}{|c|c|S|}
\hline
Genre & Name & {Weight}\\\hline
Humain & Aragorn & 102 \\\hline
\multirow{4}{*}{Hobbit}&Frodon & 32.1\\\cline{2-3}
    &Sam & 3.2 \\\cline{2-3}
    &Peregrin & 2.232\\\cline{2-3}
    &Meriadoc & 23 \\\hline
Elfe&Legolas & 34.5 \\\hline
\end{tabular}\\[1cm]


You can also use the power of booktabs and siunitx:\\
\begin{tabular}[ht]{l c S} % alignment l = left, c = centre, S = at decimal - needs siunitx
\toprule
Genre&Name& {Weight}\\  % protect non numbers with {} in S columns
\midrule
Elfe&Legolas & 34.5\\
Dwarf&Peter & 103.31\\
\bottomrule
\end{tabular}\\[1cm]

And combine that with your table:\\
\begin{tabular}{c c S}
\toprule
Genre & Name & {Weight}\\\midrule
Humain & Aragorn & 102 \\\midrule
\multirow{4}{*}{Hobbit}&Frodon & 32.1\\\cline{2-3}
    &Sam & 3.2 \\\cline{2-3}
    &Peregrin & 2.232\\\cline{2-3}
    &Meriadoc & 23 \\\midrule
Elfe&Legolas & 34.5 \\
\bottomrule
\end{tabular}


\end{document}

Answer 1

By default the standalone class doesn't make paragraphs. However, with the varwidth option it does; so

\documentclass[varwidth,convert]{standalone}

will do what you want, adjusting the width to the longest line.