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Original question

Is there any automated or semi-automated way of tracing outermost outline or whole path of letters in TikZ?

That I would be able (e.g. by using positioned nodes) to draw a letter using a letters, like shown below in my ascii-art (agreed, not really an art in this case):

   aaaaaaaa
  aaaaaaaaaa
 aa        aa 
            aa
   aaaaaaaa aa
  aaaaaaaaaaaa
 aa        aaa
 aaaaaaaaaaaaa
  aaaaaaaaa  aa

Comment

Martin's note made me certain what I already suspected, that within PGF/TikZ I am unable to trace any glyph from any font. IOW getting outline of glyph in a format supported by TikZ is a separate issue, rather not TeX-related, but worth being mentioned here.

Preliminary

Obtaining glyph outline

Let me summarize already mentioned techniques toward getting it to TikZ:

Obtaining glyph "filling"

It's something I wasn't asking at all, but it's other interesting idea that was brought up in answers:

  • convert for exporting glyph to text form and sed for cleaning it (provided by Jake)

Revised question

Mentioned earlier tracing is now part of preliminary process, as glyph outline (which can be any other path, but I'll stick with this particular example) is assumed to be known, so question should be rephrased.

What are the techniques available in TikZ to outline (fill) glyph outline with text [like one letter]?

Support for diversification of outline/fill style depending on "density" and in-path "neighborhood" (e.g. style changing in case of serifs, bent parts, etc. would be a nice feature.

I'm mostly interested in TikZ, but if you want to share non-TikZ solutions, do it immediately!

Supplementary question

If you know or just came up with not described yet method of obtaining glyph outline (or "filling") and you think it's interesting or simply worth to be mentioned, tell us about it.


Afterword, i.e. paragraph about myself

Maybe I should add that I'm really new to PGF/TikZ. Even though I was using LaTeX for about ~8 years already (with various frequency, so I am far from being an expert), I never really get to TikZ. Back in the old days I did some work with PSTricks, but frankly speaking I forgot all of that since then. I saw TikZ examples a few years ago and was amazed how PGF/TikZ can provide nice abstractions for performing different drawing tasks. Lately I had to touch TikZ and meanwhile I started to think about using it in less common way, i.e. for creating some "artistic" drawings instead of plain diagrams, sketches and whatever it is used usually. PGF/TikZ manual is great, no question, but you must know what to look for and even if you know that, your wording maybe not exactly the same as used in the documentation, which makes finding sometimes hard (it's true especially for non-native English speaker, as in my case). You may say: just browse it! Sure, but ~700 pages is pretty much, so it's rather not something you will read and understand well even within month (correct me if I am wrong). Sorry for too long OT paragraph, but it should clear some things, because it's not like I am unwilling to look to manual myself, just sometimes it's far more productive to ask experts, because they have invaluable things that cannot be found in manual - experience and better intuition!

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2  
No not really, TeX itself doesn't have much idea about the fonts. All it needs are the font metrics (width, height, depth) of each letter and things like ligatures etc. The outlines of the letters are not known to TeX and therefore to TikZ. You would need to load the outlines somehow by yourself. –  Martin Scharrer Jun 24 '11 at 22:17
    
@Martin: Thanks for confirming what I suspected. Any suggestion to how perform (as easily as possible) loading particular font outlines and converting them to TikZ compatible paths? –  przemoc Jun 24 '11 at 22:22
    
Sorry, no idea. Fonts are not my specialty. –  Martin Scharrer Jun 24 '11 at 22:24
2  
To the answerers: Note that if a question is worth answering it is most likely also worth up-voting. I still miss a few up-votes here ;-) (5 answers so, 4 up-votes, but vote is from me) –  Martin Scharrer Jun 25 '11 at 18:40
2  
@przemoc: As Leo Liu mentioned - "The key is the outline itself". I won't write an answer, but here: Your question has nothing to do with TikZ, just learn FreeType 2. Yes, if you get the points, rendering them in TikZ is just trivial. There are 3 types of fonts - Metafont, PS Type 1, True Type. For Metafont read MetaFog: Converting METAFONT Shapes to Contours, for the other - FreeType 2. SVG fonts use quadratic Bezier curves, while PS Type 1 fonts use cubic Bezier curves - information is lost. Rasterizing depends on if the hints are used. –  Karl Karlsson Jun 25 '11 at 22:28

5 Answers 5

up vote 28 down vote accepted

Update 2012-04-10: There's a preliminary package for this on the TeX-SX Launchpad site. You need to run tex on the file pgflibraryshapes.letters.dtx to produce the TikZ/PGF libraries. To generate the font files themselves, you need x2svg.pe font (uses fontforge) to convert to SVG format and svgtopgf.pl font.svg prefix > <fontname>-<fontshape>-paths.tex to convert the SVG to PDF paths (the prefix should be of the form letter@<fontname>@<fontshape>@). Take a look at letter-shapes-test.tex for a sample. The normal and italic shapes for the STIX fonts are already converted. Due to the licensing, they are called stikz!


Do you want something like this?

traced letters

Here's the source code:

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{%
  svg.path,
  decorations.text,
}

\begin{document}

\begin{tikzpicture}[scale=.3]
\draw[decorate,decoration={text along path,text={AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA}}] svg "M707 0h-255v19c36 0 43 2 55 9c8 4 14 15 14 24c0 15 -7 42 -19 70l-41 94h-262l-46 -114c-5 -13 -9 -30 -9 -42c0 -31 22 -41 70 -41v-19h-199v19c58 6 67 27 126 167l206 488h20l246 -563c28 -65 42 -86 94 -92v-19zM447 257l-116 275l-115 -275h231z";
\draw[xshift=25cm,decorate,decoration={text along path,text={aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa}}] svg "M442 66v-28c-30 -38 -56 -48 -90 -48c-37 0 -59 20 -64 73h-1c-53 -60 -102 -73 -145 -73c-62 0 -105 38 -105 104c0 52 31 91 70 117c30 20 67 39 180 81v54c0 62 -33 90 -78 90c-40 0 -70 -22 -70 -49c0 -18 6 -21 6 -42c0 -19 -20 -41 -46 -41c-21 0 -43 19 -43 46
c0 26 16 58 51 80c28 18 70 30 115 30c56 0 94 -16 118 -45s28 -50 28 -111v-191c0 -46 13 -66 31 -66c16 0 26 5 43 19zM287 127v141c-62 -22 -103 -43 -128 -66c-24 -22 -34 -46 -34 -77c0 -53 30 -77 69 -77c20 0 41 5 58 16c29 20 35 34 35 63z";
\end{tikzpicture}
\end{document}

The method of producing this was fairly straightforward. I loaded the font in fontforge and exported it as an SVG font. That then gave me the fonts as SVG paths. Since TikZ can accept SVG format, I could then cut and paste that in to a TikZ document. That lot could be done beforehand so that there was a file with the paths already specified.


Edit (2012-01-29): I had occasion to want to do this with fairly arbitrary letters so semi-automated it. It's not "production" ready, as there's still the odd bit needed to make it truly usable with no extra tweaking, but it's at the usable-if-you-know-what-you're-doing stage.

  1. Convert the font to SVG. You need fontforge installed. Then the following script, made executable, will invoke fontforge and convert the font specified on the command line to SVG format (output saved in the current directory). Eg if it is saved as x2svg.pe (note the extension) then run as x2svg.pe /path/to/font/amazing-font.otf.

    #! /usr/bin/fontforge -script
    
    Open($1)
    Generate($1:t:r + ".svg")
    
  2. Extract the glyph paths from the resulting XML file. The following Perl script does a reasonable job: it should trim excess whitespace at the start and end as well. Also, one could do with a better naming scheme (I tried unicode, but that got confusing).

    perl -MXML::Twig -e '
    $xml = XML::Twig->new(
    twig_handlers => {
    glyph => sub { $n = $_->{att}{"glyph-name"}; $n =~ s/_//g; print  %% "\\svgletter{" . $n  . "}{" . $_->{att}{d} . "}\n";}
    }
    );
    $xml->parsefile("amazing-font.svg");
    ' > amazing-font.letters.tex
    
  3. Then in the TeX file, we just need to input this file and use the paths. Here's an example:

    \documentclass{article}
    \usepackage{tikz}
    \usetikzlibrary{svg.path}
    \newcommand\svgletter[2]{%
      \expandafter\def\csname svgglyph#1\endcsname{svg "#2"}
    }
    
    \input{TeXGyreSchola-Bold.letters}
    
    \def\STOP{stop}
    \def\NOTHING{}
    \def\empty{}
    \newcommand\outline[1]{%
    \outlinelet#1\STOP}
    
    \let\thisis\newpage
    
    \newcommand\vfillornewpage{%
      \ifx\thisis\vfill
      \let\thisis\newpage
      \else
      \let\thisis\vfill
      \fi
      \thisis}
    
    \newcommand\outlinelet[1]{%
      \let\next=\vfillornewpage
      \ifx#1\STOP
      \else
      \tikz[baseline=0pt] \draw[scale=0.09,ultra thick] \csname svgglyph#1\endcsname;
      \let\next=\outlinelet
      \fi
      \next}
    
    
    \begin{document}
    
    \outline{Outline}
    
    \end{document}
    

    With result:

    outlined font in TikZ

    Obviously, one could be more adventurous in the actual use of the path. Also, it would be good to have a more systematic way of getting the right scale factor (perhaps measuring the height of an "x"). Don't expect kerning!

share|improve this answer
    
Great answer, so far the closest one to what I was looking for. Thank you very much, Andrew! –  przemoc Jun 25 '11 at 18:23
1  
@przemoc: Can you be more specific about what you want to do with the trace? I can see lots of potential with this in TikZ so would be happy to play a bit more. –  Loop Space Jun 25 '11 at 18:46
    
@Andrew: I've updated the question. Hope it will help you in playing a bit more. :) –  przemoc Jun 25 '11 at 20:57
1  
@Karl: Fortunately, the font that I used was a TrueType font which uses quadratic bezier curves so in this case, no information was lost. Facetiousness aside, you are correct. Nonetheless, there comes a point at which precision has to give way to expediency. –  Loop Space Jun 26 '11 at 17:46
1  
I've just had occasion to revisit this, working with the STIX fonts, and one thing I found was that the SVGs produced by fontforge use cubic beziers. So no information is lost. –  Loop Space Apr 10 '12 at 9:20

Since you want to fill the letter with discrete nodes, you don't actually need a vector shape of the outline: A raster will suffice. Here's a one line script that compiles a LaTeX document containing just the required letter, uses ImageMagick to rasterise the resulting pdf and output it in text format, and finally cleans it up using a sed command:

pdflatex -jobname "letter" "\documentclass{standalone} \begin{document} a \end{document}" && \
convert -density 300 letter.pdf txt:- | \
sed -e '1d' -e '/white/d' -e 's/:.*//' -e 's/,/ /g' > letter.txt;

The resulting letter.txt file can then be plotted using pgfplots (or plain TikZ, but that would require a bit of looping) with the mark=text option:

\documentclass{article}

\usepackage{pgfplots}

\begin{document}
\raisebox{3mm}{\scalebox{24}{a}} %For comparison
\begin{tikzpicture}
\begin{axis}[y dir=reverse,
    only marks,
    width=7cm,
    axis equal,
    hide axis=true]
\addplot [mark=text,text mark=a] table {letter.txt};
\end{axis}
\end{tikzpicture}

\end{document}

ascii art with latex!

share|improve this answer
    
I don't want to fill letter using letters, just outline it using them. I know, my ascii-art wasn't good enough, so looking only at it you could be easily misguided. Anyway, I'm aware of some image to ascii-art converters, yet I didn't think about using them at all. Your solution is so simple, yet so smart! Kudos! –  przemoc Jun 25 '11 at 9:07
    
Rasterization depends on the algorithm used. For sure font renderers use different rasterization algorithms than ImageMagic, so the result will differ. And also the font renderer uses square dots, but not general rectangle shapes. I think, ImageMagic can't read the fonts hinting. But if it can - than the result will not be based on the outline. –  Karl Karlsson Jun 26 '11 at 10:52
    
@Karl: In the approach I outlined above, ImageMagick is not at all aware of what it is rasterising, so it definitely doesn't take into account font hinting. As far as ImageMagick is concerned, the object to be rasterised is just a general picture. I'm not entirely sure what you mean with your remark about the square dots -- ImageMagick just turns the PDF into a raster image, so the picture elements will be square pixels. The result is most certainly not based on the outline -- I had misunderstood what przemoc was trying to achieve. In essence, I just presented a way of producing TeX ASCII art. –  Jake Jun 26 '11 at 12:10
    
You have 5 "natural" ways to anchor a pixel - 4 corners and 1 center. The same goes for the letters. So we have 25 "natural" ways of rasterizing and arranging the letters. And of course, infinitely many "unnatural" ways. Even in the limit of infinite rasterization resolution we still have 5 "natural" ways to anchor a letter. These 5 anchoring will produce different images. And the letters aren't square like pixels. –  Karl Karlsson Jun 26 '11 at 15:00

Without TikZ but with pdf-trans.tex from texlive but I'm not sure of this code . It's my first experiment with pdf-trans

\documentclass[11pt]{article} 
\input pdf-trans
\font\f=qx-lmr10    at 60pt
\newbox\qbox

\def\outline#1{%
\setbox\qbox\hbox{\f #1}%
\boxgs{2 Tr 0.8 g}{}\copy\qbox
}%
\pagestyle{empty}
\parindent=0pt

\begin{document}

 \outline{Alter}

\end{document} 

enter image description here

share|improve this answer
    
@przemoc This works only with pdftex, I think. –  Alain Matthes Jun 25 '11 at 15:21
    
Nice finding. Even if I don't see how it could be useful in my case (I wasn't asking for general outline technique), it's good to know about such package existence. Its example.pdf shows many nice features, which pdf-trans brings to LaTeX. BTW For ~6 years already I'm using pdflatex only, so such requirement is ok for me. –  przemoc Jun 25 '11 at 15:39
    
Very nice, but is it possible to get word wrap in multiline text? Without that feature the utility is limited. –  mmj Apr 15 '13 at 14:45
    
@mmj Not possible with the definition of \outline. With a multiline text, perhaps it's possible to apply the macro to each word with a loop or someting like this but I'm not sure. I'm not a great expert of TeX. –  Alain Matthes Apr 15 '13 at 17:28

If you want to manipute the outline, PSTricks (pst-text package) or Asymptote may be better choice.

The document of pst-text shows how to use it in detail. Note that it can be only compiled with latex + dvips. For example

% latex + dvips + ps2pdf
\documentclass{article}
\usepackage{pst-text}
\DeclareFixedFont{\LBR}{T1}{hlh}{m}{n}{2cm}% Lucida Bright
\begin{document}
\pstextpath{%
  \pscharpath*[linestyle=none,fillstyle=solid,fillcolor=lightgray]
    {\LBR R}}{rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr}
\end{document}

enter image description here

In Asymptote, you can use function

path[] texpath(Label L);

to get the path of the letter easily. Asymptote has fewer restrictions than PSTricks, you can use pdfLaTeX or XeLaTeX with it. For example:

settings.tex="xelatex";
usepackage("fontspec");
texpreamble("\setmainfont{Lucida Bright}");
path[] R = texpath(Label("R", fontsize(6cm), align=Align));

fill(R, lightgray);

for (path p: R) {
    real len = arclength(p);
    for (real i = 0; i < len; i += 10pt) {
        label("r", arcpoint(p, i));
    }
}

enter image description here

share|improve this answer
    
Thanks for your effort. I am no longer using pstricks. I heard about Asymptote before, so maybe I'll touch it in future. I wasn't interested in outline per se though, but it's nice to see another method to obtain it. –  przemoc Jun 25 '11 at 18:18
    
@przemoc: The key is the outline itself. It is much easier to use the path. Since tikz itself cannot (impossible) extract the outline of the character from the font, there won't be a pure tikz solution. –  Leo Liu Jun 25 '11 at 18:30
    
Yes, I understood it quite early, just after Martin's comment. Yet, as I've written in comment below my question, I am grateful for all answers, even not strictly answering my question. Even though I am no longer PSTricks and dvips user, I upvoted your answer, because you're on topic and I did not strictly limited expected answers to TikZ world only. Sure, tag suggests it, but it's not like violating it is a crime. :) –  przemoc Jun 25 '11 at 18:41
    
@przemoc: Yes. If you must use tikz, you can use pstoedit or other tools (like fontforge that Andrew uses) to extract the path for tikz. –  Leo Liu Jun 25 '11 at 18:52

I dont know about TikZ, but you can get a pstricks outline by using Inkscape. Input the text and then select and copy it to bitmap. You can trace the bitmap (Inkscape uses Potrace internaly) and export the graphics to Latex with pstricks macros.

enter image description here


The pstricks output is then

enter image description here

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2  
You can use the extention called inkscape2tikz(code.google.com/p/inkscape2tikz) to obtain the tikz code. –  Azoun Jun 25 '11 at 4:50
    
@Azoun: Thank you both! @Danie: Rasterization and tracing worsen a bit quality and there is no reason to do it. After exporting plain letter you can just change \pscustom options: set line style, avoid filling, etc. @Azoun: This extension is actually more interesting than I thought, because it stores text literally unless you perform conversion Object to Path. –  przemoc Jun 25 '11 at 9:30

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