How to make fonts available to the LaTeX interpreter in Matlab R2013a?

Question

It is possible to embed LaTeX-formatted text and equations into Matlab plots by setting the text property 'Interpreter' to the value 'latex', e.g.

text(0.1, 0.5, 'Einstein: $E = m c^2$', ...
    'Interpreter', 'latex', 'FontSize', 32)

These equations appear on screen as well as in illustrations exported to eps files.

Through the appropriate LaTeX commands, it is also possible to change the font from the default Computer Modern Serif to e.g. Computer Modern Typewriter

text(0.1, 0.5, '\fontfamily{cmtt}\selectfont Einstein: $E = m c^2$', ...
    'Interpreter', 'latex', 'FontSize', 32)

My question is: Is it possible to insert additional fonts into the Matlab installation, such that these fonts become available for use with 'Interpreter' 'latex', for rendering on screen as well as producing eps files? And if yes, how?

Background

(All paths relative to the Matlab installation, /opt/MATLAB/R2013a on my Linux system.)

Matlab includes a customized version of the (La)TeX interpreter. It is called via a frontend m-file called tex.m in toolbox/matlab/graphics which takes LaTeX code as an argument and returns dvi data within its output argument. The customized LaTeX installation is found in sys/tex and includes TeX font metric files under sys/tex/tfm.

I do not have any information on the parts of Matlab that render this dvi. However, font data for rendering are found under sys/fonts/ttf and sys/fonts/type1.

Making additional fonts usable therefore consists of two parts: Making it available for the LaTeX interpreter, and making it available for the rendering function. The first part can be tackled by manipulating tex.m, such that it generates the dvi through an independent regular installation of LaTeX, and installing the font to this LaTeX in the usual way (e.g. font packages). See undocumentedmatlab.

The second part of the question is therefore the crucial one: How to insert additional fonts into sys/fonts/ttf and sys/fonts/type1 such that they become usable by the dvi renderer component of Matlab.

Concrete case

I tried to concretely solve the second problem for a special case: The Computer Modern Sans font is included in the Matlab-LaTeX installation through tex/tfm/cmss10.tfm, but the corresponding ttf and pfb-files are missing from sys/fonts such that it does not get rendered.

Matlab's collection of ttf-files does not appear to have some kind of inventory. I therefore simply copied the file cmss10.ttf from an installation of matplotlib to sys/fonts/ttf/cm/mwa_cmss10.ttf, following the file and folder naming conventions of the other files present. This procedure was reported to be working on Alec's Web Log for Matlab 2011b on Max OS X, but on my system it has no effect, neither for screen display nor eps export.

Matlab's collection of type1 fonts has a complex inventory, distributed over files fonts.dir, fonts.scale, encodings.dir and a folder encodings full of enc-files. Again I found cmss10.pfb, this time from a TeXlive installation, renamed and copied it, and made entries in the inventory files following the example of the other fonts listed. Again, this procedure has no effect at all.

Does anyone know more about how Matlab uses ttf and pfb-files, and can give me a hint on how to make the cmss10-files accessible to Matlab rendering? Or does anyone have a suggestion how to debug this and find out more about the inner workings of Matlab's LaTeX support?

Answer 1

I invested hours of further research into my question, and came up with some interesting new insights, but no real solution. Still, I'm posting my results here in order for others who might investigate this to start from. I post it as an "answer" not make my already long question even longer.

Comparison between Matlab's old (R2010a) and current (R2013a) tex and fonts infrastructure

For the standard font Computer Modern Roman, the old infrastructure contains

sys/tex/tfm/cmr10.tfm
sys/fonts/ttf/cm/cmr10.ttf
sys/fonts/type1/cm/cmr10.pfb
sys/fonts/type1/cm/cmr10.pfm

and the current

sys/tex/tfm/cmr10.tfm
sys/fonts/ttf/cm/mwa_cmr10.ttf
sys/fonts/ttf/cm/mwb_cmr10.ttf
sys/fonts/type1/cm/mwa_cmr10.pfb
sys/fonts/type1/cm/mwb_cmr10.pfb

The TeX font metric files are identical. The truetype and type1 files appear to contain the same glyph data, but have been split into files containing latin (mwa) and greek characters (mwb). The pfm file has simply disappeared.The old type1 files have a copyright notice 1997 by the AMS, the new ones 2011 by the MW.

This indicates that in order to make Computer Modern Sans from an old Matlab work in current Matlab, it might be sufficient to copy cmss10.ttf and cmss10.pfb to mwa_cmss10.ttf and mwa_cmss10.pfb, since the tfm file is still present (see question).

Which files are used in R2013a?

The additional dir and enc files in sys/fonts/type1 appear not to be used, because deleting them leaves screen rendering and eps generation fully functional.

I suspected that the ttf files are used for screen rendering and the pfb files for inclusion in generated eps files. The former appears not to be the case, because deleting all ttf files leaves screen rendering and eps generation fully functional, too. Matlab does complain, however, if the folder sys/fonts/ttf/cm does not exist!

This indicates that a) it's not necessary to bother with modifying the dir and enc files, and b) it's not necessary to copy the ttf file.

Is inserting new pfb files enough?

After cmss10.pfb from an old Matlab is copied to sys/fonts/type1/cm/mwa_cmss10.pfb, using Computer Modern Sans in an equation still makes Matlab warn that "cmss10 is not supported", and the screen rendering is not correct. Moreover, a generated eps file does not render correctly.

However, the generated eps file does include the contents of mwa_cmss10.pfb and the reason it doesn't work is that the included pfb file defines a font named "CMSS10", while the eps refers to a font named "mwa_cmss10". Instead of @Daniel E. Shub's solution to change the references in the eps, one can edit the file mwa_cmss10.pfb and change its \FontName to "mwa_cmss10". This might be done with a simple text editor applied to the pfb. However, the better way is to disassemble the pfb file to PostScript using t1disasm, change the PostScript, and then reassemble using t1asm. These tools are contained in the t1utils package on CTAN.

The resulting eps does still not work properly though: Characters are not correctly positioned, especially for larger font sizes.

This indicates that the presence of the pfb file alone does not provide Matlab with the correct font metrics, and that the dvi file generated by Matlab's LaTeX does not explicitly position characters but relies on the renderer having those metrics.

See tex.se for a question concerning a workaround for the second point.

Does "hacking" existing fonts work?

Daniel E. Shub proposed in his answer not to add fonts, but to overwrite those existing in the Matlab installation. There are two problems with this:

– The correct font metrics are still not available to Matlab. Overwriting a font therefore only works, and only approximately, if the metrics of the original font and those of the new one are similar.

Example:

– Screen rendering only works in some cases. For me, overwriting mwa_cmr10 with a patched cmss10 and using \rm did lead to Computer Modern Sans being rendered to screen and in the eps file, albeit with slightly wrong positioning. However, overwriting mwa_cmtt10 and using \tt did not lead to Computer Modern Sans being rendered on screen; instead, Computer Modern Typewriter was rendered.

This implies a) that there is another independent source of font metrics for Matlab's renderer. As far as I can tell, they come from none of the files under sys/tex or sys/fonts. b) Font outlines are only in some cases read from the pfb files in sys/fonts/type1/cm.

Conclusion

The inner workings of the dvi renderer in recent Matlab therefore remain mysterious. Possible candidates where the missing information may be hidden are toolbox/matlab/graphics/hardcopy.p and / or com/mathworks/hg/uij/TextRasterizer.class in java/jar/hg.jar.

I'll cease my investigations for the time being (and going to have a look at psfrag ;)