[OS X TeX] Documents less legible with T1 font encoding

[Bruno Voisin]

Le 4 août 05 à 20:34, Armin Goralczyk a écrit :

> Why is it that if I use T1 font encoding instead of OT1 documents  
> are less legible in Preview.app, TeXniscope, and Adobe Acrobat  
> unless enlarged? Printing is fine, so there is no real problem with  
> the output, but it's not really comfortable if documents are not  
> legible in full page preview, so I still use OT1 for preliminary  
> work and T1 only for final output.

By default, LaTeX in OT1 encoding uses the Computer Modern fonts (aka  
CM fonts) which are included in gwTeX in PostScript form (in /Library/ 
teTeX/share/texmf.tetex/fonts/type1/bluesky/), yielding documents  
which not only are legible in PDF viewers but are also fast to display.

In T1 encoding the situation is different: by default LaTeX uses the  
European Computer Modern fonts (aka EC fonts) which are only included  
in gwTeX in MetaFont form (in /Library/teTeX/share/texmf.tetex/fonts/ 
source/jknappen/). As a consequence, at the end of a LaTeX run  
MetaFont is invoked in the background, to generate bitmap  
representations of the fonts, in PK format, and then these bitmap  
fonts are included in the final PDF output. Because these are bitmap,  
and hence resolution-dependent, these fonts yield ugly preview and  
take ages to display; however, the resolution of these bitmaps being  
generally those appropriate for most common printers, the final  
printed version is fine.

[In case you're willing to dig further, the different "modes" setting  
the way the PK fonts are created, and in particular their resolution,  
are defined in /Library/teTeX/share/texmf.tetex/metafont/misc/ 
modes.mf. The default mode is ljfour, corresponding to the 600dpi  
LaserJet 4 printer.]

There are two solutions to this problem:

- Install the CM-Super fonts (there is an i-Package for them), which  
include PostScript versions of the EC fonts. These will be installed  
in /Library/teTeX/share/texmf.local/fonts/type1/public/cm-super/.  
Once the fonts are installed, you only need to specify in the  
preamble of your LaTeX document:

     \usepackage[T1]{fontenc}
     \usepackage{textcomp}

- Use the Latin Modern fonts (aka LM fonts), which are another  
PostScript version replacing the EC fonts. They are part of gwTeX,  
and are installed inside /Library/teTeX/share/texmf.tetex/fonts/type1/ 
public/lm/. They are invoked by calling the lmodern package, as follows:

     \usepackage[T1]{fontenc}
     \usepackage{textcomp}
     \usepackage{lmodern}

You might prefer the LY1 encoding to T1 (I do, as (i) it was designed  
for maximum compatibility with the Windows default font encoding, and  
is hence less prone to create problems in PDF files, and (ii) it  
avoids the use to virtual fonts), in which case you would use instead:

     \usepackage[LY1]{fontenc}
     \usepackage{lmodern}

[Again in case you're interested by more details, the CM-Super fonts  
were created from the sources of the EC fonts by (1) using MetaFont  
to create bitmaps of each character at high resolution, then (ii) by  
tracing the pixels to convert these bitmaps to PostScript code. On  
the other hand, the Latin Modern fonts were -- and still are, it's a  
work-in-progress -- created by applying MetaPost, a variant of  
MetaFont producing not PK bitmap output but PS vectorial output, to  
the sources of the EC fonts to generate PostScript fonts directly.  
Hence, the Latin Modern are supposed to be of better quality than the  
CM-Super, though I am nothing close to competent to assess this.]

[And even more details, in case you're *really* interested: The  
production of the PostScript CM fonts included in gwTeX used the same  
tracing procedure as for the CM-Super fonts. However, while for the  
CM-Super fonts the process was entirely automatic, for the CM fonts  
the results were extensively post-processed manually, to correct any  
tracing error and to add hinting. This work was done by two  
companies, Blue Sky Research and Y&Y, which were the respective  
developers of the commercial Textures for Mac OS and Y&Y TeX for  
Windows; the fonts were later made freely available by a consortium  
involving AMS, SIAM, Elsevier, IBM and Springer; Y&Y is now defunct  
while Blue Sky Research has become Blue Sky TeX Systems]

Hope you'll still find this post useful despite the number of details,

Bruno Voisin--------------------- Info ---------------------
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