[Tex/LaTex] Torn page effect

typography

[See Torn paper: matching up the torn edges for more on this topic, as well as better illustrations of the final product.]

I have a document with a lot of short excerpts from another book scattered through it. Putting frames around them looks a little too 'clean'. How can I get a 'torn page' type effect, to make it look as if the excerpt has been physically torn out of a book? (I've occasionally seen this done in printed books, although I can't find an example right now.)

I'm not wedded to a very specific look here — Googling 'torn page' gives plenty of examples. But just to give this some frame of reference, here are some of the nicer ones:

enter image description here

http://www.vectorstock.com/i/composite/84,79/white-paper-rip-edge-vector-198479.jpg

enter image description here

http://lh6.ggpht.com/-eO-uRyGeA_0/TUkzCMuwuJI/AAAAAAAAB6E/2och4rP0l88/386–x–277–torn-paper.jpg

(The strong colouration in this second example is a probably a little too distracting for actual use, although it might be interesting as an option. It's more the edge effect I'm interested in.)

enter image description here

Edit (again): I tried typesetting my text according to the updated versions of the answers below. Here are the results:

enter image description here

Or with interpolated shading:
http://people.ds.cam.ac.uk/mg262/combined2.pdf

Best Answer

Not exactly the result you wanted, but it can be a starting point. It combines framed and tikz packages. The idea can lead to further improvements.

Framed-tikz

See http://www.texample.net/tikz/examples/framed-tikz/ (btw, I'm the author)

UPDATE: Playing with the idea of a fractal decoration, and also with shaded paper and blurred drop shadows, I got the following results. Currently the implementation still does not use framed, so it is restricted to the case in which the framed paragraph does not break among pages.

Results

\documentclass[a5paper]{article}
\usepackage{lipsum}   % To generate test text 
\usepackage{framed}
\usepackage{tikz}
\usepackage[margin=1cm]{geometry}% for screen preview
\usetikzlibrary{decorations.pathmorphing,calc,shadows.blur,shadings}
\pgfmathsetseed{1} % To have predictable results
% Define a background layer, in which the parchment shape is drawn
\pgfdeclarelayer{background}
\pgfsetlayers{background,main}

% This is the base for the fractal decoration. It takes a random point between the start and end, and
% raises it a random amount, thus transforming a segment into two, connected at that raised point
% This decoration can be applied again to each one of the resulting segments and so on, in a similar
% way of a Koch snowflake.
\pgfdeclaredecoration{irregular fractal line}{init}
{
  \state{init}[width=\pgfdecoratedinputsegmentremainingdistance]
  {
    \pgfpathlineto{\pgfpoint{random*\pgfdecoratedinputsegmentremainingdistance}{(random*\pgfdecorationsegmentamplitude-0.02)*\pgfdecoratedinputsegmentremainingdistance}}
    \pgfpathlineto{\pgfpoint{\pgfdecoratedinputsegmentremainingdistance}{0pt}}
  }
}

% define some styles
\tikzset{
   paper/.style={draw=black!10, blur shadow, shade=bilinear interpolation,
                 lower left=black!20, upper left=black!15, upper right=white, lower right=black!10},
   irregular border/.style={decoration={irregular fractal line, amplitude=0.2},
           decorate,
     },
   ragged border/.style={ decoration={random steps, segment length=7mm, amplitude=2mm},
           decorate,
   }
}

% Macro to draw the shape behind the text, when it fits completly in the
% page
\def\tornpaper#1{
\tikz{
  \node[inner sep=1em] (A) {#1};  % Draw the text of the node
  \begin{pgfonlayer}{background}  % Draw the shape behind
  \fill[paper] % recursively decorate the bottom border
        decorate[irregular border]{decorate{decorate{decorate{decorate[ragged border]{
        ($(A.south east) - (0, random*5mm)$) -- ($(A.south west) - (0, random*5mm)$)
        }}}}}
        -- (A.north west) -- (A.north east) -- cycle;
  \end{pgfonlayer}}
}


\begin{document}
\noindent
\tornpaper{
\parbox{.9\textwidth}{\lipsum[11]}
}

\bigskip
\noindent
\tornpaper{
\parbox{.9\textwidth}{\lipsum[15]}
}
\end{document}

NOTE Some pdf viewers (eg. Sumatra) have issues to display the interpolated shading used in the last examples.

UPDATE See also the related question Torn paper: matching up the torn edges

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