Creating CAPTCHAs and other fancy distorted letters with TikZ

Question

I try to do a little more spectacular that phrase ( Δελτιο Υλης) . Is the headline on a press material for my students. The fact is that I could accomplish this with gimp or a graphics program such as the inscape or similar programs.

But what I want is to make a somewhat artistic distortion of letters through tikz to show to my students the possibilities of having the LaTeX without using external programs.

My question: is there a way to warp letter and how?

Currently this is what I've done ... and certainly I have not artistic vein ...

enter image description here

\documentclass[b5paper,svgnames,10pt]{book}
\usepackage[utf8x]{inputenc}
\usepackage{tikz}
\usepackage{color}
\usepackage{xcolor}
\begin{document}
\begin{tikzpicture}
\draw[grid,step=0.5cm,gray,very thin] (-1cm,-1cm) grid (9cm,1.5cm);
\node[scale=5.,color =MidnightBlue ] at (0,0) {$\Delta$};
\node[scale=5.,color =MidnightBlue ,rotate=30] at (0.84cm,0.1cm) {$\varepsilon$};
\node[scale=5.,color =MidnightBlue,rotate=-15 ] at (1.3cm,0.0cm) {$\lambda$};
\node[scale=5.,color =MidnightBlue,rotate=+15 ] at (1.95cm,-0.2cm) {$\tau$};
\node[scale=5.,color =MidnightBlue ] at (2.5cm,0) {$\iota$};
\node[scale=5.,color =MidnightBlue ] at (2.6cm,0.4cm) {$'$};
\node[scale=5.,color =MidnightBlue ] at (3.0cm,0) {$o$};
\node[scale=6.,color =MidnightBlue,rotate=-20 ] at (5.3cm,0.08cm) {$\Upsilon$};
\node[scale=5.,color =MidnightBlue ] at (6.cm,-0.2cm) {$\lambda$};
\node[scale=5.,color =MidnightBlue ] at (7.cm,-0.1cm) {$\eta$};
\node[scale=5.,color =MidnightBlue ] at (8.cm,0) {$\varsigma$};
\end{tikzpicture}
\end{document}

@percusse What I want to do is advertise LaTeX not the word ... :) — karathan, Mar 29 '13 at 23:08
Did you see one of our greatest questions about Ctulhu and random rotations of letters here http://tex.stackexchange.com/q/29402/3235 ? Or any other great answers on this site ? — percusse, Mar 29 '13 at 23:11
@karathan: Looks like a CAPTCHA to me. Maybe it would make sense to rename the question to accommodate that? — Count Zero, Mar 29 '13 at 23:18
@percusse No, I had not seen this question. Thanks for the suggestion — karathan, Mar 29 '13 at 23:20
You are using Greek mathematical letters. The minuscules are (as they should) in their italic shape. I recommend to browse the {greek} tag on how to properly use Greek letters. — Qrrbrbirlbel, Mar 30 '13 at 04:11
@karathan: How about 'Creating CAPTCHAs and other artistically distorted letters with TikZ'? — Count Zero, Mar 30 '13 at 09:00
Maybe I should add that I meant the terrible quality of Word math rendering that it comes this horrible by default if one uses Word. — percusse, Mar 30 '13 at 15:33
Why limit the question to TikZ? (see Why Metapost discrimination) — Aditya, Mar 30 '13 at 17:12

Mark Wibrow · Accepted Answer · 2013-04-04T10:01:00.233

No claims to artistry or anything (you may, or may not notice that I've changed the text :-), also as it involves randomness sometimes it looks OK sometimes it does not:

\documentclass{standalone}
\usepackage{tikz}

\pgfmathdeclarerandomlist{fonts}{{\bf}{\tt}{\rm}{\sf}{\it}{\sl}}

\tikzset{
    distort/.style={
        rotate=rand*10, 
        yslant=rand/3, 
        xslant=rand/3, 
        xscale=1+rand/4,
        yscale=1+rand/4,
        execute at begin node={%
            \pgfmathrandomitem{\newfont}{fonts}\newfont%
        }
    }
}

% Need a special space because inside \node { };
% \ignorespaces and \unskip will remove spaces.
\def\bigspace{\hbox to 1ex{\hfil}}

\begin{document}

\Huge

\begin{tikzpicture}

% The basic idea is to create a node called 0
% then by maintaining indexes \i = 1,2,... and \j = 0,1,...
% it is possible to position the current node (called \i)
% to the previous node (called \j).
\coordinate (0);
\foreach \letter [count=\i, count=\j from 0]in {P,i,g,s, \bigspace  ,m,i,g,h,t, \bigspace ,f,l,y}
    \node [inner sep=0pt, anchor=base west, distort]  at (\j.base east) (\i)
        {\pgfmathrandomitem{\newfont}{fonts}\newfont\letter};

\tikzset{yshift=-0.75in}


% The opacity is stored in an array and accessed
% using the (undocumented) evaluate key.
\foreach \c [evaluate={\o={5,25, 100}[\c-1];}]in {1,...,3} {
    \coordinate (0) at (rand/4, rand/4);
    \foreach \letter [count=\i, count=\j from 0]in {P,i,g,s, \bigspace  ,m,i,g,h,t, \bigspace ,f,l,y}
        \node [inner sep=0pt, anchor=base west, black!\o, distort]  at (\j.base east) (\i) {\letter};
}

\tikzset{yshift=-0.75in}

% In order to get the same randomness (!) the random seed
% can be set to a fixed value. In this case the value is
% selected from the range 1-32768.
\pgfmathrandominteger\seed{1}{32768}
\foreach \c [evaluate={\o={5,25, 100}[\c-1];}]in {1,...,3} {
    \coordinate (0) at (\c*2pt,\c*2pt);
    \pgfmathsetseed{\seed}
    \foreach \letter [count=\i, count=\j from 0]in {P,i,g,s, \bigspace  ,m,i,g,h,t, \bigspace ,f,l,y}
        \node [inner sep=0pt, anchor=base west, black!\o, distort]  at (\j.base east) (\i) {\letter};
}
\end{tikzpicture}

\end{document}

catchpa

EDIT: Added some more randomness in an attempt to make it more fancy.

Really an excellent result. LaTeX and Tikz have a unique way to surprise me!!! and all of you with your codes — karathan, Mar 31 '13 at 14:00
If you find a little time, would be easy to put a short comment on each line to explain your code — karathan, Mar 31 '13 at 18:52
Is there any way to get the text that is displayed to make it an actual captcha? (Sorry, TeX n00b) — Cole Tobin, Apr 05 '13 at 19:49

Aditya · Answer 2 · 2013-03-31T05:28:27.393

21

Here is a solution that uses Metapost and ConTeXt (no font changes but randomized color and scaling):

\starttext
\startMPpage[offset=3mm]

picture lab;

numeric total_width, current_width;

total_width := 0;

for s = "H", "e", "l", "p", "\quad", "Γ", "Δ" :
   lab := textext(s); 
   current_width := xpart (lrcorner lab - llcorner lab);

  for i = 1,3,2 :
   draw lab  rotated (-30 randomized 60) shifted (total_width randomized 5pt, i*6pt randomized 2pt)
      if i = 1 :
        scaled (0.8 randomized 0.2)
        withcolor (0.8 randomized 0.1, 0.8 randomized 0.1, 0.8 randomized 0.2)
      elseif i = 2 :
        scaled (0.8 randomized 0.2)
        withcolor (0.2 randomized 0.1, 0.1 randomized 0.1, 0.8 randomized 0.2)
      else :
        scaled (0.8 randomized 0.2)
        withcolor (0.8 randomized 0.1, 0.8 randomized 0.1, 0.8 randomized 0.2)
      fi;
  endfor

   total_width := total_width + current_width ;
endfor


\stopMPpage

\stoptext

which gives

enter image description here

edited Mar 31 '13 at 05:28

answered Mar 30 '13 at 17:43

Aditya

62,301

something went wrong as all three colors are light. One of them (in the middle) is supposed to be dark. – Aditya Mar 31 '13 at 05:03
No, context filename is correct. But the colors are changed at random, so there is no way to predict the output. – Aditya Mar 31 '13 at 05:12
Hmm... strange. I uploaded a bigger picture. – Aditya Mar 31 '13 at 05:29
Yes. Indeed. I might try to re-install ConTeXt. Well, thanks for the answer. This is really helpful. +1 :) – hpesoj626 Mar 31 '13 at 05:32
Although I use LaTeX + Tikz... is a very good result and will be useful to users of Metapost and ConTeXt – karathan Mar 31 '13 at 14:07
@karathan: The code does not use any ConTeXt sepecific features and will work with LaTeX + emp as well. – Aditya Mar 31 '13 at 15:23
@Aditya What is 'emp' . I do not know what is. – karathan Mar 31 '13 at 18:31
@karathan: see http://tex.stackexchange.com/questions/tagged/emp It allows you to embed metapost code in LaTeX. – Aditya Mar 31 '13 at 18:56
@Aditya I will try to experiment – karathan Mar 31 '13 at 19:12

score 13 · Answer 3 · answered Mar 30 '13 at 19:35

Without PSTricks.

enter image description here

\documentclass[preview,border=12pt]{standalone}
\usepackage[a0paper]{geometry}
\usepackage[nomessages]{fp}
\usepackage{graphicx}
\usepackage{pgffor}
\FPseed=0
\begin{document}
\foreach \C in {I,a,m,a,p,i,g,.}{%
    \FPrandom\Scale\FPeval\Scale{round(Scale*10+1:2)}
    \FPrandom\Rotate\FPeval\Rotate{round(Rotate*1000:2)}
    \FPrandom\Raise\FPeval\Raise{round(Raise*10:2)}
    \scalebox{\Scale}{\rotatebox{\Rotate}{\raisebox{\Raise pt}{\C}}}%
}%
\end{document}

Creating CAPTCHAs and other fancy distorted letters with TikZ

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