Given file.tex
\documentclass[
convert={
density=300 -alpha deactivate,
outext=.png
},
]{standalone}
\begin{document}
\begin{tabular}{|c|c|}
\hline
a & b \\ \hline
c & d \\ \hline
\end{tabular}
\end{document}
when I ran pdflatex -shell-escape file with
ImageMagick 6.9.3-4 Q16 x86_64 2016-02-29
I got a transparent background.
After upgrading to
ImageMagick 6.9.4-4 Q16 x86_64 2016-06-29
I now get a full A4 page (for both pdf and png), with a page number, but with a white background.
In both cases I'm running TeX Live 2015 on OS X 10.11.5.
What could be going wrong? How might upgrading ImageMagick have affected the pdflatex step that precedes convert?
Update
Logging in from a new user account on OS X, everything works fine. So I figured that it's just the difference between the two ~/.bash_profile. After using a single export PATH line in the ~/.bash_profile in both accounts and confirming that I am indeed running the same two executables from both accounts:
$ which pdflatex
/Library/TeX/texbin/pdflatex
$ which convert
/opt/local/bin/convert
the problem persists. (I am aware that this is no longer a TeX issue. I can delete the question if you like.)


-alpha deactivateswitches transparency off, surely? – cfr Jun 29 '16 at 23:40standaloneclass that maybe is causing different displays on different software versions. @cfr Can you confirm the bug in case you have texstudio installed? Tx. – alwaysask Jun 30 '16 at 00:55