Can we extract the points making the character from the font file?

Question

Rather than tracing the border of a magnified character to find some critical points making the character as follows,

\documentclass[pstricks,border=12pt]{standalone}
\usepackage{pst-text,pst-eucl}

\DeclareFixedFont{\ps}{U}{psy}{m}{n}{12cm}% the symbol font
\DeclareFixedFont{\PS}{T1}{ptm}{m}{n}{11cm}% the times font

\def\x{4}

\psset
{
    showpoints=true,
    linecolor=red,
    PointName=none,
    dotscale=0.5,
}

\newpsstyle{gridstyle}
{
    subgriddiv=10,
    subgridcolor=lightgray,
    subgridwidth=0.05pt,
    subgriddots=0,
    gridcolor=black,
    gridwidth=0.1pt,
    griddots=0,
    gridlabels=5pt,
    gridlabelcolor=red,
}
\begin{document}

\begin{pspicture}[showgrid](-\x,\x)(\x,-\x)
    \rput(0,0){\pscharpath[linecolor=blue,linewidth=0.1pt]{\PS R}}
    \pstGeonode
    (-3.483, 3.700){n1}
    (-0.800, 3.700){n2}
    ( 1.260, 3.700){c1}
    ( 2.340, 3.200){c2}
    ( 2.340, 1.700){n3}

    \psline(n1)(n2)
    \psbezier(n2)(c1)(c2)(n3)
\end{pspicture}

\end{document}

I want to extract such points directly from the font file.

Is it possible to do that?

The objective is to recreate such a character to be used for clipping discussed in my previous question How to fill a region bounded by a character and a graphic object with a color?

Answer 1

Here's the steps needed to convert a font character to a PGF path. It works on a Unix-based system (tested on Linux and MacOSX). I don't know if the required programs are available on other systems. The dependencies are FontForge and Perl. The former is fairly important, the latter is just the non-TeX language I know best.

1. Use FontForge to convert the font to SVG paths. You can do this in FontForge, or simply run the following script on the font file: x2svg.pe /path/to/font/font.ttf (ttf simply for example, FontForge reads everything, save script as x2svg.pe or change the calling command appropriately).

   #! /usr/bin/env fontforge
   
   Open($1)
   Generate($1:t:r + ".svg")
   

2. Run the perl script svgtopgf.pl on the resulting file. Syntax is svgtopgf.pl font.svg prefix where prefix is to make the resulting stuff unique. This creates a file that defines a load of paths, one for each glyph, and also contains their bounding box information. The paths, and bounding boxes, are labelled according to the decimal unicode number. The path commands are PGF basic layer commands.

Then use these macros to define the relevant paths and the rest of the TikZ/PGF code to manipulate them as you wish. At the TeX-SX launchpad there's a PGF library that makes these letters into node shapes.

Answer 2

No, not without a lot of work.

At the postscript level you can convert the letter to a path and fill it or clip with it rather than stroke (draw) it. So you can for example do:

from this postscript (which you could convert to pstricks calls easily)

  gsave                                      % Save old clip path
    /Times-Roman findfont 350 scalefont setfont
    200 200 moveto (R) true charpath    % Set up the text's path
  gsave 0.8 1.8 scale 350 180 100 0 360 arc  eofill grestore

    grestore
  showpage

However you want to go further and find the points of intersection between the path extracted from R and the path of the ellipse, and work out which of those points go with which region. That is hard; requiring some equations to be solved. Probably more the preserve of metapost than postscript or tex but its a long time since I looked at that.