In my Windows build of emacs, when I put the cursor in a latex equation and
run

M-x org-toggle-latex-fragment


then things chug along for a second but then fail.  In the *Org Preview
LaTex Output* buffer, I see the message:

This is dvipng 1.15 Copyright 2002-2015 Jan-Ake Larsson
[1
dvipng: Fatal error, cannot open output file
c:/Users/scott/AppData/Local/Temp/"orgtex4628hQG.png


The reason for the failure is the leftover quote (...Temp/"orgtex...) in
the expected png output file.  With some hackery, I can see that the
command that's being run is:

dvipng -fg "rgb 0 0 0" -bg "rgb 1 1 1" -D "102.0" -T tight -o
"c:/Users/scott/AppData/Local/Temp/""orgtex4628hQG".png
"c:/Users/scott/AppData/Local/Temp/orgtex4628hQG.dvi"


If I paste that into a cygwin xterm, it runs fine on the .dvi file that's
still in the Temp directory.  But the command fails in a Windows cmd
window; if I remove the extra quotes, then the command works in the cmd
window too.

The extra quote comes from the default customization for the dvipng
image-converter field of org-preview-latex-process-alist:

dvipng -fg %F -bg %B -D %D -T tight -o %o%b.png %f


where the %o%b part of the customization concatenates two strings that are
already quoted. That's OK for *nix but apparently not for Windows.

I don't see a way to change the customization to fix this; can anyone take
a look at the elisp?

Thanks,

Scott

--- A test org file --------------

* Put cursor in the equation below and type C-c C-x C-l

\[
e^{i\pi} = -1
\]

--- My setup ---------------
Emacs  : GNU Emacs 25.1.1 (i686-w64-mingw32) of 2016-09-17
Package: Org mode version 9.0.1 (9.0.1-elpaplus @
c:/Users/scott/OneDrive/scotto/.emacs.d/elpa/org-plus-contrib-20161118/)


current state:
==============
(too huge to send)