Re: [Matplotlib-users] How to mix maths & text in labels ?

[William H. <wh...@gm...>]

Hi list

On Wed, 2005-06-01 at 13:25 -0500, John Hunter wrote:
> >>>>> "Chris" == Chris Barker <Chr...@no...> writes:
> 
>     Chris> Wonderful! this is great news. How have you done it? Have
>     Chris> you written a DVI driver? or do you use TeX and associated
>     Chris> tools to create a bitmap and put that on the image? Or
>     Chris> something else?
> 
> For *Agg, we use tex + dvipng and load the output as a transparent,
> anti-aliased raster, caching the dvipng output in ~/.tex.cache for
> efficiency.  For PS, we use tex + dvips + psfrag + latex + a patched
> ps2epsi.  The latter is cumbersome, but it works.  In an ideal world,
> we would simply use tex + dvips but embedding the postscript fragments
> generated by dvips in arbitrary locations on the figure, but this has
> proved challenging.
> 

Have you looked at how PyX (http://pyx.sourceforge.net/) handles things?
They have excellent support for tex/latex labels and it seems to be
implemented in a much "cleaner" way than you describe above. As far as I
can see, they run a single TeX job containing all the strings from the
current plot (see the texrunner class in pyx/text.py) and then parse the
dvi output themselves (see pyx/dvifile.py)

> Having our own dvi parser would be a nice solution.  As you noted, the
> format isn't too complicated, except for the font handling and the
> fact that you need your own bytecode processing engine to extract the
> information.  We're waiting until Robert Kern has another boring
> experiment to site through for this one.

Well, PyX is GPLed so I don't see why you couldn't adopt their DVI
parser. One thing you need to bear in mind if you are using TeX to
generate PS output is that the resultant files will probably be
unacceptable to many scientific journals without further processing. The
production staff generally try to open the PS files in Adobe Illustrator
and this causes multiple problems with files generated both by PyX and
by dvips. The solution is to convert all fonts to outlines before
submission (and also make sure all bbox coords are +ve). You can do this
with recent versions of ghostscript:

 gs -dBATCH -dNOPAUSE -dSAFER -q -sDEVICE=epswrite -dEPSFitPage \
    -sOutputFile=new.eps old.eps

I suppose I should introduce myself since I haven't posted to this list
before. I've been looking at various python scientific plotting packages
for the last few months. I'm currently using gnuplot (supplemented by
bash or python scripting) for interactive use and quick hacks, together
with PyX for publication-quality output. Matplotlib looks very
interesting since I think it could potentially replace both gnuplot and
PyX. The features it seemed to be lacking the last time I looked in any
detail (v 0.70) were

1. Good, flexible support for reading data from files

2. Publication-quality text handling for math and accented characters
(i.e., full LaTeX support)

It looks like you have now addressed point 2 at least, so I've just
downloaded 0.81alpha from CVS and I'll see how it goes. The big
advantages matplotlib has over PyX in my opinion are a more intuitive
API and a larger/more-active developer pool and user base.  
   
Best wishes

Will

-- 
  Dr William Henney, Centro de Radioastronomía y Astrofísica,
  Universidad Nacional Autónoma de México, Campus Morelia