Example: Fitting text to a shape

% Fitting text to a shape
% Author: Paul Gaborit
\documentclass{article}
\usepackage[english]{babel}
\usepackage{blindtext}
\usepackage[T1]{fontenc}
\usepackage{shapepar}
\usepackage{microtype}
\usepackage{tikz}
\usetikzlibrary{calc,fit,intersections}
\def\shapeparnodeaccuracy{2}
\newcommand\shapeparnode[6][]{
  % 6 parameters:
  % style for node (default:empty),
  % h margin, v margin, left path, right path, text (just one paragraph!)

  % name left and right paths and compute there bounding boxes
  \begin{scope}[local bounding box=leftbb]
    \path[name path global=left, xshift=#2] #4;
  \end{scope}
  \node[inner ysep=-#3, inner xsep=0pt, fit=(leftbb)](leftbb){};
  \begin{scope}[local bounding box=rightbb]
    \path[name path global=right, xshift=-#2] #5;
  \end{scope}
  \node[inner ysep=-#3, inner xsep=0pt, fit=(rightbb)](rightbb){};

  % global bounding box
  \path let
  \p1=(leftbb.north west), \p2=(leftbb.south west),
  \p3=(rightbb.north east), \p4=(rightbb.south east)
  in
  \pgfextra{
    \pgfmathsetmacro{\ymin}{(\y1 < \y3) ? \y1 : \y3}
    \pgfmathsetmacro{\ymax}{(\y2 > \y4) ? \y2 : \y4}
    \typeout{ymin \ymin}
    \typeout{ymax \ymax}
  } node[inner sep=0, fit={(\x1,\ymin pt)(\x3,\ymax pt)}](mybb){};

  % compute nb steps
  \path let \p1=(mybb.north), \p2=(mybb.south) in
  \pgfextra{
    \pgfmathsetmacro{\fnthght}{1em/\shapeparnodeaccuracy}
    \pgfmathtruncatemacro{\nbsteps}{(\y1-\y2)/\fnthght}
    \xdef\nbsteps{\nbsteps}
    \typeout{nb steps \nbsteps}
  };

  % horizontal references
  \path (mybb.north) -- (mybb.south)
  \foreach \cnt in {0, 1, ..., \nbsteps}{
    \pgfextra{\pgfmathsetmacro{\pos}{\cnt/\nbsteps}}
    coordinate[pos=\pos] (ref \cnt)
  };

  % left and right boundaries coordinates
  \foreach \cnt in {0, 1, ..., \nbsteps}{
    % an horizontal line from left to right
    \path[name path=ltor]
      (mybb.west |- ref \cnt) --  (mybb.east |- ref \cnt);
    % same line from right to left
    \path[name path=rtol]
      (mybb.east |- ref \cnt) -- (mybb.west |- ref \cnt);
    % left boundary
    \path[name intersections={of=rtol and left, by={l \cnt}, sort by=rtol}];
    % right boundary
    \path[name intersections={of=ltor and right, by={r \cnt}, sort by=ltor}];
  }
  % start point (and initial value of boundshape)
  \path let \p1=(l 0) in 
  \pgfextra{
    \pgfmathsetmacro{\xstart}{\x1}
    \xdef\boundshape{{0}{0}b{\xstart}}
    \xdef\xmin{\xstart}
    \xdef\xmax{\xstart}
  };

  % top and bottom
  \path let \p1=(l 0), \p2=(l \nbsteps) in
  \pgfextra{
    \pgfmathsetmacro{\ystart}{\y1}\xdef\ystart{\ystart}
    \pgfmathsetmacro{\yending}{\y2}\xdef\yending{\yending}
  };
  % incremental definition of boundshape
  \foreach \cnt in {0, 1, ..., \nbsteps}{
    \path let \p1=(l \cnt), \p2=(r \cnt) in
    \pgfextra{
      \pgfmathsetmacro{\start}{\x1}
      \pgfmathsetmacro{\len}{\x2-\x1}
      \pgfmathsetmacro{\ypos}{\cnt/\nbsteps*(\ystart - \yending)}
      {\let\\=\relax \xdef\boundshape{\boundshape\\{\ypos}t{\start}{\len}}}
      \pgfmathsetmacro{\xmin}{(\xmin < \start) ? \xmin : \start}
      \xdef\xmin{\xmin}
      \pgfmathsetmacro{\xmax}{(\xmax > \start + \len) ? \xmax : \start + \len}
      \xdef\xmax{\xmax}
    };
  }
  % draw the node with text in a shapepar
  \pgfmathsetmacro{\ymax}{\ystart - \yending}
  {\let\\=\relax \xdef\boundshape{\boundshape\\{\ymax}e{0}}}
  \node[#1, text width=\xmax pt - \xmin pt, align=flush left,
  anchor=north west, inner sep=0]
  at (mybb.north west -| \xmin pt, 0)
  {\Shapepar[1pt]{\boundshape}#6\par};
}

\begin{document}%
\begin{tikzpicture}
  \begin{scope}[yshift=-22cm] % third example
    \footnotesize
    \def\radius{3.1}
    \def\pathone{(3,0)
      arc(90:225:\radius)
      arc (45:-45:\radius/2.415)
      arc(135:270:\radius)}
    \def\pathtwo{(3,-4*\radius)
      arc(-90:0:\radius)
      arc(180:90:\radius)
      arc(270:180:\radius)
      arc(0:90:\radius)}
    \fill[top color=lime, bottom color=orange, middle color=yellow, draw=white]
    \pathone -- \pathtwo -- cycle;
    \shapeparnode[text=black, font=\footnotesize]
      {2em}{1em}{\pathone}{\pathtwo}{\blindtext[2]}%
    %\draw[orange] \pathone;
    %\draw[orange] \pathtwo;
  \end{scope}
\end{tikzpicture}
\end{document}