[Insight-developers] About Postscript to PDF quality

[Luis Ibanez]

Hi,

Some hints about the quality of PDF documents generated
from PostScript using ps2pdf.

from :

    http://www.adobe.com/support/techdocs/543e.htm

The low quality of the PDF on the example is not due to
LaTeX itself, but to the options used in ps2pdf. LaTeX
generates DVI (device independent) files that can be
rendered at different levels of quality.

PDF files need to indicate in some way the type of font
they are using. The default option on ps2pdf and dvi2pdf
is to use Type3 fonts. 

Type3 fonts are basically bitmaps that are included in the 
PDF file itself. The advantage of doing so is that you are 
sure that the document is selfcontained, and it can be 
viewed by anyone because the fonts are provided. 

The disadvantage is that the resolution of these fonts is 
fixed. This use to be OK for printing but not that good for 
viewing on screen.

A second option is to use Type1 fonts, which are scalable.
In this case the font definition is not included in the PDF
file and you have to rely on the readers having those fonts
installed in their machines in order to be able to read the
file.  (Which, BTW is the same case for MS-Word documents).
This files have a much better quality rendered on screen,
but can be very frustrating when you don't have the specific
fonts installed.  This is not a big problem is the font used 
are 'common', or are made available in some other way.

dvi2pdf and ps2pdf can be configured to specify which fonts
should be used as Type1 and which as Type3, so a document
can contain a mix of both.


Luis