Give LaTeX images a maximum width using the prelude only

src/Text/Pandoc/Writers/LaTeX.hs

@@ -338,7 +338,7 @@ inlineToLaTeX (Link txt (src, _)) =
                          char '}'
 inlineToLaTeX (Image _ (source, _)) = do
   modify $ \s -> s{ stGraphics = True }
-  return $ text $ "\\includegraphics{" ++ source ++ "}" 
+  return $ text $ "\\includegraphics{" ++ source ++ "}"
 inlineToLaTeX (Note contents) = do
   st <- get
   put (st {stInNote = True})

templates/latex.template

@@ -50,6 +50,15 @@ $if(url)$
 $endif$
 $if(graphics)$
 \usepackage{graphicx}
+% We will generate all images so they have a width \maxwidth. This means
+% that they will get their normal width if they fit onto the page, but
+% are scaled down if they would overflow the margins.
+\makeatletter
+\def\maxwidth{\ifdim\Gin@nat@width>\linewidth\linewidth
+\else\Gin@nat@width\fi}
+\makeatother
+\let\Oldincludegraphics\includegraphics
+\renewcommand{\includegraphics}[1]{\Oldincludegraphics[width=\maxwidth]{#1}}
 $endif$
 \usepackage[breaklinks=true,unicode=true]{hyperref}
 \setlength{\parindent}{0pt}

tests/writer.latex

@@ -14,6 +14,15 @@
 \newcommand{\textsubscr}[1]{\ensuremath{_{\scriptsize\textrm{#1}}}}
 \usepackage{url}
 \usepackage{graphicx}
+% We will generate all images so they have a width \maxwidth. This means
+% that they will get their normal width if they fit onto the page, but
+% are scaled down if they would overflow the margins.
+\makeatletter
+\def\maxwidth{\ifdim\Gin@nat@width>\linewidth\linewidth
+\else\Gin@nat@width\fi}
+\makeatother
+\let\Oldincludegraphics\includegraphics
+\renewcommand{\includegraphics}[1]{\Oldincludegraphics[width=\maxwidth]{#1}}
 \usepackage[breaklinks=true,unicode=true]{hyperref}
 \setlength{\parindent}{0pt}
 \setlength{\parskip}{6pt plus 2pt minus 1pt}