On Wed, Jul 31, 2002 at 02:02:48PM -0700, lcrocker(a)nupedia.com wrote:
I've
hacked the phpwiki code to add a new namespace
[[math: ]] so you can write formulas like [[math:a^2+b^2=c^2]] or
[[math:\sum_{n=0}^{\infty}\frac{1}{n}=\infty]].
The code will make TeX create an image (PNG) of the formula. Those
images will be cached, they will be created only once and will be
shared between articles. ( [[math:E=m c^2]] might be used on many
pages ).
That's almost exactly what I had in mind; only I think it would be
better for the back end to have to have a spearate process
communicating with the Wiki code over IPC--the "TeX server"--
which will take formulas and return images, out of a cache if
they've been rendered already, calling TeX to render them if needed.
The cache will be indexed by a hash function on a canonicalized
text of the expression.
The wiki end of this won't be hard. The other server is the real
work. I'm afraid I can't take on that project right now, but if
that server gets built, I'll be happy to call it.
Hi,
I moved this to wikitech-l since it will be much to detailed for
wikipedia-l.
The code is ready. It doesn't use IPC, no client/server. It only
exec's a shell script.
The PHP script creates a tempfile with suffix .tex and calls a
shellscript with the name of the tempfile as a parameter.
The script
- renders TeX to DVI using LaTeX
- converts DVI to eps using dvips
- renders eps to PNG using convert from ImageMagick
- removes all tempfiles created by LaTeX
The .png has the same name as the .tex. The name is the
MD5-Hash of the formula. The .png will placed in an
image directory of the webserver, in my implementation
it's /upload/, but should probably be different, e.g.
/upload/math/.
The PHP code than adds the formula and the name of the
image file to a new table in the database. Using this
cache it decides whether to render a formula.
It then replaces [[math:formula]] by
<img src="/upload/imagename.png" alt="formula"
align="middle">
(OK, using the TeX-Formula as alt-text is not always really
readable, but always better than no alt-text at all)
The only thing still to be done is preparing some TeX preamble to
prevent something like
[[math:\mbox{\include{"/etc/passwd"}}]]
Alternatively, everything could be installed chroot, but
this would have to include Apache and PHP and LaTeX.
The shell script looks like this:
#!/bin/sh
exec >> /tmp/tex2png.log
exec 2>&1
set -x
cd /tmp
echo $*
cat $1
echo
latex $1
dvips -E $1
convert -density 110 $1.ps $1.png
cp $1.png /home/jf/wiki/phpwiki/newcodebase/upload/
chmod a+r /home/jf/wiki/phpwiki/newcodebase/upload/$1.png
rm ${1}*
$1 is the hashcode of the formula.
Providing the diff of the PHP-code would take a little
time - I have to remove my attempts in wiki-table-markup
first.
For an example see
http://jeluf.mine.nu/jf/newcodebase/wiki.phtml?title=Triangle
but please keep in mind - it's a 486/DX2 66 with 20 MB RAM,
a machine I normaly use for fetching mail only.
Regards,
JeLuF
