# Computer Modern not raster. Why?

The fonts produced by METAFONT should be raster rather than vector, as far as I know. The Computer Modern font is produced by METAFONT, hence it should be raster. The following code

\font\testfont= cmr10 at 100pt

\testfont Abcdefghi

\bye


anyhow produces a document that seems to include a vector font, when given to pdftex or tex+dvipdf. Why?

• Why do you think this should be raster? (just wondering) – daleif Mar 24 at 20:18
• @daleif See here tex.stackexchange.com/questions/107489/… – User Mar 24 at 20:20
• What does mention why your code should be raster if vector version of cmr10 exists – daleif Mar 24 at 20:22
• @daleif How has the vector version been produced? – User Mar 24 at 20:40
• the default map files in texlive and miktex specify type1 versions of cm. There are by now several methods of converting metafont files, the cm conversions were originally proprietary done by blue sky research for textures but released some decades ago now in conjunction with the AMS. – David Carlisle Mar 24 at 21:07

You can de-activate the mapping cmr10 to Type1 font in pdftex by \pdfmapline command:

\pdfmapline{-cmr10}

\font\f=cmr10

\f Hello world.

\end


Now, the pk bitmap is used, which looks horrible in typical PDF viewers. If the pk is not present, then pdftex runs Metafont in order to create it. This is method used before the year 1990 (more or less). You can return to these old days using \pdfmapline, as shown above. IMHO, there is no reason to do this (with the exception of conducting historical research).

• Fully agree. The pk fonts are undoubtedly superior because they can be adapted to the output device and would look probably better on a high resolution device if the mode_setup is done carefully. But for everyday usage, the Type1 fonts produced by BlueSky are quite good as well: as you observe, pk files at screen resolution are terrible, because PDF viewers convert them to Type3 fonts. – egreg Mar 27 at 17:56
• egreg agreeing with you, how strange :) – User Mar 28 at 7:18
• How is the resolution of the rasterisation chosen? Is it defined in the metafont file for cmr? – User Mar 28 at 8:32
• It was just for "historical research", not for real applications. Yes, the pdf viewers produce ugly results. One that seems to produce reasonable results is mupdf – User Mar 28 at 8:36
• To be clear for those who may not know, the raster font “looks horrible in typical PDF viewers” only at typical low resolutions (because the vector fonts come with hinting instructions that specify how to “cheat” low resolution). If you print (typical printers have higher resolution than monitors), or view it on a sufficiently high resolution monitor, or zoom in so that more pixels are available for each letter, then the raster font looks fine (and in principle even better). – ShreevatsaR Apr 5 at 22:25