Support non-transparent backgrounds

[dehnert]

In some situations, it's nice to have a non-transparent background (eg, the image will be shown on top of both a white background and something dark, and rather than finding a foreground that'll work with both you just want a white box as your background regardless).

It would be nice if the API supported an option for keeping the background in place.

For example,

{
	'code': '\begin{document} Hello \end{document}',
	'format': 'pdf',
        'background': 'opaque' [or default, 'transparent']
}

I think an opaque background is just a matter of adding to ~COMMAND_IMG_CONVERT in jobs.py '-alpha', 'deactivate' before the -density 200 when requested.

If you think this would be useful / would be willing to take such a change, I'd be happy to put together a PR (but figured checking before writing it might make sense, and probably won't have a chance for a couple days).

(And thanks for this tool!)

[dxsmiley]

This is an interesting idea, but don't think it's required to add it explicitly to the API.

You can use the pagecolor package to achieve a similar effect:

\documentclass{article}
\usepackage{pagecolor}
\begin{document}
\pagecolor{orange}
Hello, world!
\end{document}

I think just using the colour white should be sufficient?