NAME
    GraphViz - Interface to the GraphViz graphing tool

SYNOPSIS
      use GraphViz;

      my $g = GraphViz->new();

      $g->add_node('London');
      $g->add_node('Paris', label => 'City of\nlurve');
      $g->add_node('New York');

      $g->add_edge('London' => 'Paris');
      $g->add_edge('London' => 'New York', label => 'Far');
      $g->add_edge('Paris' => 'London');

      print $g->as_png;

DESCRIPTION
    This module provides an interface to layout and image generation of
    directed and undirected graphs in a variety of formats (PostScript, PNG,
    etc.) using the "dot", "neato", "twopi", "circo" and "fdp" programs from
    the GraphViz project (http://www.graphviz.org/ or
    http://www.research.att.com/sw/tools/graphviz/).

  What is a graph?
    A (undirected) graph is a collection of nodes linked together with
    edges.

    A directed graph is the same as a graph, but the edges have a direction.

  What is GraphViz?
    This module is an interface to the GraphViz toolset
    (http://www.graphviz.org/). The GraphViz tools provide automatic graph
    layout and drawing. This module simplifies the creation of graphs and
    hides some of the complexity of the GraphViz module.

    Laying out graphs in an aesthetically-pleasing way is a hard problem -
    there may be multiple ways to lay out the same graph, each with their
    own quirks. GraphViz luckily takes part of this hard problem and does a
    pretty good job in a couple of seconds for most graphs.

  Why should I use this module?
    Observation aids comprehension. That is a fancy way of expressing that
    popular faux-Chinese proverb: "a picture is worth a thousand words".

    Text is not always the best way to represent anything and everything to
    do with a computer programs. Pictures and images are easier to
    assimilate than text. The ability to show a particular thing graphically
    can aid a great deal in comprehending what that thing really represents.

    Diagrams are computationally efficient, because information can be
    indexed by location; they group related information in the same area.
    They also allow relations to be expressed between elements without
    labeling the elements.

    A friend of mine used this to his advantage when trying to remember
    important dates in computer history. Instead of sitting down and trying
    to remember everything, he printed over a hundred posters (each with a
    date and event) and plastered these throughout his house. His spatial
    memory is still so good that asked last week (more than a year since the
    experiment) when Lisp was invented, he replied that it was upstairs,
    around the corner from the toilet, so must have been around 1958.

    Spreadsheets are also a wonderfully simple graphical representation of
    computational models.

  Applications
    Bundled with this module are several modules to help graph data
    structures (GraphViz::Data::Dumper), XML (GraphViz::XML), and
    Parse::RecDescent, Parse::Yapp, and yacc grammars
    (GraphViz::Parse::RecDescent, GraphViz::Parse::Yapp, and
    GraphViz::Parse::Yacc).

    Note that Marcel Grunauer has released some modules on CPAN to graph
    various other structures. See GraphViz::DBI and GraphViz::ISA for
    example.

    brian d foy has written an article about Devel::GraphVizProf for Dr.
    Dobb's Journal:
    http://www.ddj.com/columns/perl/2001/0104pl002/0104pl002.htm

  Award winning!
    I presented a paper and talk on "Graphing Perl" using GraphViz at the
    3rd German Perl Workshop and received the "Best Knowledge Transfer"
    prize.

        Talk: http://www.astray.com/graphing_perl/graphing_perl.pdf
      Slides: http://www.astray.com/graphing_perl/

METHODS
  new
    This is the constructor. It accepts several attributes.

      my $g = GraphViz->new();
      my $g = GraphViz->new(directed => 0);
      my $g = GraphViz->new(layout => 'neato', ratio => 'compress');
      my $g = GraphViz->new(rankdir  => 1);
      my $g = GraphViz->new(width => 8.5, height => 11);
      my $g = GraphViz->new(width => 30, height => 20,
                            pagewidth => 8.5, pageheight => 11);

    The most two important attributes are 'layout' and 'directed'.

    layout
        The 'layout' attribute determines which layout algorithm GraphViz.pm
        will use. Possible values are:

        dot The default GraphViz layout for directed graph layouts

        neato
            For undirected graph layouts - spring model

        twopi
            For undirected graph layouts - radial

        circo
            For undirected graph layouts - circular

        fdp For undirected graph layouts - force directed spring model

    directed
        The 'directed' attribute, which defaults to 1 (true) specifies
        directed (edges have arrows) graphs. Setting this to zero produces
        undirected graphs (edges do not have arrows).

    rankdir
        Another attribute 'rankdir' controls the direction the nodes are
        linked together. If true it will do left->right linking rather than
        the default up-down linking.

    width, height
        The 'width' and 'height' attributes control the size of the bounding
        box of the drawing in inches. This is more useful for PostScript
        output as for raster graphic (such as PNG) the pixel dimensions can
        not be set, although there are generally 96 pixels per inch.

    pagewidth, pageheight
        The 'pagewidth' and 'pageheight' attributes set the PostScript
        pagination size in inches. That is, if the image is larger than the
        page then the resulting PostScript image is a sequence of pages that
        can be tiled or assembled into a mosaic of the full image. (This
        only works for PostScript output).

    concentrate
        The 'concentrate' attribute controls enables an edge merging
        technique to reduce clutter in dense layouts of directed graphs. The
        default is not to merge edges.

    random_start
        For undirected graphs, the 'random_start' attribute requests an
        initial random placement for the graph, which may give a better
        result. The default is not random.

    epsilon
        For undirected graphs, the 'epsilon' attribute decides how long the
        graph solver tries before finding a graph layout. Lower numbers
        allow the solver to fun longer and potentially give a better layout.
        Larger values can decrease the running time but with a reduction in
        layout quality. The default is 0.1.

    overlap
        The 'overlap' option allows you to set layout behavior for graph
        nodes that overlap. (From GraphViz documentation:)

        Determines if and how node overlaps should be removed.

        true
            (the default) overlaps are retained.

        scale
            overlaps are removed by uniformly scaling in x and y.

        false
            If the value converts to "false", node overlaps are removed by a
            Voronoi-based technique.

        scalexy
            x and y are separately scaled to remove overlaps.

        orthoxy, orthxy
            If the value is "orthoxy" or "orthoyx", overlaps are moved by
            optimizing two constraint problems, one for the x axis and one
            for the y. The suffix indicates which axis is processed first.

            NOTE: The methods related to "orthoxy" and "orthoyx" are still
            evolving. The semantics of these may change, or these methods
            may disappear altogether.

        compress
            If the value is "compress", the layout will be scaled down as
            much as possible without introducing any overlaps.

        Except for the Voronoi method, all of these transforms preserve the
        orthogonal ordering of the original layout. That is, if the x
        coordinates of two nodes are originally the same, they will remain
        the same, and if the x coordinate of one node is originally less
        than the x coordinate of another, this relation will still hold in
        the transformed layout. The similar properties hold for the y
        coordinates.

    no_overlap
        The 'no_overlap' overlap option, if set, tells the graph solver to
        not overlap the nodes. Deprecated, Use 'overlap' => 'false'.

    ratio
        The 'ratio' option sets the aspect ratio (drawing height/drawing
        width) for the drawing. Note that this is adjusted before the size
        attribute constraints are enforced. Default value is "fill".

        numeric
            If ratio is numeric, it is taken as the desired aspect ratio.
            Then, if the actual aspect ratio is less than the desired ratio,
            the drawing height is scaled up to achieve the desired ratio; if
            the actual ratio is greater than that desired ratio, the drawing
            width is scaled up.

        fill
            If ratio = "fill" and the size attribute is set, node positions
            are scaled, separately in both x and y, so that the final
            drawing exactly fills the specified size.

        compress
            If ratio = "compress" and the size attribute is set, dot
            attempts to compress the initial layout to fit in the given
            size. This achieves a tighter packing of nodes but reduces the
            balance and symmetry. This feature only works in dot.

        expand
            If ratio = "expand" the size attribute is set, and both the
            width and the height of the graph are less than the value in
            size, node positions are scaled uniformly until at least one
            dimension fits size exactly. Note that this is distinct from
            using size as the desired size, as here the drawing is expanded
            before edges are generated and all node and text sizes remain
            unchanged.

        auto
            If ratio = "auto" the page attribute is set and the graph cannot
            be drawn on a single page, then size is set to an ``ideal''
            value. In particular, the size in a given dimension will be the
            smallest integral multiple of the page size in that dimension
            which is at least half the current size. The two dimensions are
            then scaled independently to the new size. This feature only
            works in dot.

    bgcolor
        The 'bgcolor' option sets the background colour. A colour value may
        be "h,s,v" (hue, saturation, brightness) floating point numbers
        between 0 and 1, or an X11 color name such as 'white', 'black',
        'red', 'green', 'blue', 'yellow', 'magenta', 'cyan', or 'burlywood'.

    node,edge,graph
        The 'node', 'edge' and 'graph' attributes allow you to specify
        global node, edge and graph attributes (in addition to those
        controlled by the special attributes described above). The value
        should be a hash reference containing the corresponding key-value
        pairs. For example, to make all nodes box-shaped (unless explicity
        given another shape):

          my $g = GraphViz->new(node => {shape => 'box'});

  add_node
    A graph consists of at least one node. All nodes have a name attached
    which uniquely represents that node.

    The add_node method creates a new node and optionally assigns it
    attributes.

    The simplest form is used when no attributes are required, in which the
    string represents the name of the node:

      $g->add_node('Paris');

    Various attributes are possible: "label" provides a label for the node
    (the label defaults to the name if none is specified). The label can
    contain embedded newlines with '\n', as well as '\c', '\l', '\r' for
    center, left, and right justified lines:

      $g->add_node('Paris', label => 'City of\nlurve');

    Attributes need not all be specified in the one line: successive
    declarations of the same node have a cumulative effect, in that any
    later attributes are just added to the existing ones. For example, the
    following two lines are equivalent to the one above:

      $g->add_node('Paris');
      $g->add_node('Paris', label => 'City of\nlurve');

    Note that multiple attributes can be specified. Other attributes
    include:

    height, width
        sets the minimum height or width

    shape
        sets the node shape. This can be one of: 'record', 'plaintext',
        'ellipse', 'circle', 'egg', 'triangle', 'box', 'diamond',
        'trapezium', 'parallelogram', 'house', 'hexagon', 'octagon'

    fontsize
        sets the label size in points

    fontname
        sets the label font family name

    color
        sets the outline colour, and the default fill colour if the 'style'
        is 'filled' and 'fillcolor' is not specified

        A colour value may be "h,s,v" (hue, saturation, brightness) floating
        point numbers between 0 and 1, or an X11 color name such as 'white',
        'black', 'red', 'green', 'blue', 'yellow', 'magenta', 'cyan', or
        'burlywood'

    fillcolor
        sets the fill colour when the style is 'filled'. If not specified,
        the 'fillcolor' when the 'style' is 'filled' defaults to be the same
        as the outline color

    style
        sets the style of the node. Can be one of: 'filled', 'solid',
        'dashed', 'dotted', 'bold', 'invis'

    URL sets the url for the node in image map and PostScript files. The
        string '\N' value will be replaced by the node name. In PostScript
        files, URL information is embedded in such a way that Acrobat
        Distiller creates PDF files with active hyperlinks

    If you wish to add an anonymous node, that is a node for which you do
    not wish to generate a name, you may use the following form, where the
    GraphViz module generates a name and returns it for you. You may then
    use this name later on to refer to this node:

      my $nodename = $g->add_node('label' => 'Roman city');

    Nodes can be clustered together with the "cluster" attribute, which is
    drawn by having a labelled rectangle around all the nodes in a cluster.
    An empty string means not clustered.

      $g->add_node('London', cluster => 'Europe');
      $g->add_node('Amsterdam', cluster => 'Europe');

    Clusters can also take a hashref so that you can set attributes:

      my $eurocluster = {
        name      =>'Europe',
        style     =>'filled',
        fillcolor =>'lightgray',
        fontname  =>'arial',
        fontsize  =>'12',
      };
      $g->add_node('London', cluster => $eurocluster, @default_attrs);

    Nodes can be located in the same rank (that is, at the same level in the
    graph) with the "rank" attribute. Nodes with the same rank value are
    ranked together.

      $g->add_node('Paris', rank => 'top');
      $g->add_node('Boston', rank => 'top');

    Also, nodes can consist of multiple parts (known as ports). This is
    implemented by passing an array reference as the label, and the parts
    are displayed as a label. GraphViz has a much more complete port system,
    this is just a simple interface to it. See the 'from_port' and 'to_port'
    attributes of add_edge:

      $g->add_node('London', label => ['Heathrow', 'Gatwick']);

  add_edge
    Edges are directed (or undirected) links between nodes. This method
    creates a new edge between two nodes and optionally assigns it
    attributes.

    The simplest form is when now attributes are required, in which case the
    nodes from and to which the edge should be are specified. This works
    well visually in the program code:

      $g->add_edge('London' => 'Paris');

    Attributes such as 'label' can also be used. This specifies a label for
    the edge. The label can contain embedded newlines with '\n', as well as
    '\c', '\l', '\r' for center, left, and right justified lines.

      $g->add_edge('London' => 'New York', label => 'Far');

    Note that multiple attributes can be specified. Other attributes
    include:

    minlen
        sets an integer factor that applies to the edge length (ranks for
        normal edges, or minimum node separation for flat edges)

    weight
        sets the integer cost of the edge. Values greater than 1 tend to
        shorten the edge. Weight 0 flat edges are ignored for ordering nodes

    fontsize
        sets the label type size in points

    fontname
        sets the label font family name

    fontcolor
        sets the label text colour

    color
        sets the line colour for the edge

        A colour value may be "h,s,v" (hue, saturation, brightness) floating
        point numbers between 0 and 1, or an X11 color name such as 'white',
        'black', 'red', 'green', 'blue', 'yellow', 'magenta', 'cyan', or
        'burlywood'

    style
        sets the style of the node. Can be one of: 'filled', 'solid',
        'dashed', 'dotted', 'bold', 'invis'

    dir sets the arrow direction. Can be one of: 'forward', 'back', 'both',
        'none'

    tailclip, headclip
        when set to false disables endpoint shape clipping

    arrowhead, arrowtail
        sets the type for the arrow head or tail. Can be one of: 'none',
        'normal', 'inv', 'dot', 'odot', 'invdot', 'invodot.'

    arrowsize
        sets the arrow size: (norm_length=10,norm_width=5,
        inv_length=6,inv_width=7,dot_radius=2)

    headlabel, taillabel
        sets the text for port labels. Note that labelfontcolor,
        labelfontname, labelfontsize are also allowed

    labeldistance, port_label_distance
        sets the distance from the edge / port to the label. Also labelangle

    decorateP
        if set, draws a line from the edge to the label

    samehead, sametail
        if set aim edges having the same value to the same port, using the
        average landing point

    constraint
        if set to false causes an edge to be ignored for rank assignment

    Additionally, adding edges between ports of a node is done via the
    'from_port' and 'to_port' parameters, which currently takes in the
    offset of the port (ie 0, 1, 2...).

      $g->add_edge('London' => 'Paris', from_port => 0);

  as_canon, as_text, as_gif etc. methods
    There are a number of methods which generate input for dot / neato /
    twopi / circo / fdp or output the graph in a variety of formats.

    Note that if you pass a filename, the data is written to that filename.
    If you pass a filehandle, the data will be streamed to the filehandle.
    If you pass a scalar reference, then the data will be stored in that
    scalar. If you pass it a code reference, then it is called with the data
    (note that the coderef may be called multiple times if the image is
    large). Otherwise, the data is returned:

    Win32 Note: you will probably want to binmode any filehandles you write
    the output to if you want your application to be portable to Win32.

      my $png_image = $g->as_png;
      # or
      $g->as_png("pretty.png"); # save image
      # or
      $g->as_png(\*STDOUT); # stream image to a filehandle
      # or
      #g->as_png(\$text); # save data in a scalar
      # or
      $g->as_png(sub { $png_image .= shift });

    as_debug
        The as_debug method returns the dot file which we pass to GraphViz.
        It does not lay out the graph. This is mostly useful for debugging.

          print $g->as_debug;

    as_canon
        The as_canon method returns the canonical dot / neato / twopi /
        circo / fdp file which corresponds to the graph. It does not layout
        the graph - every other as_* method does.

          print $g->as_canon;

          # prints out something like:
          digraph test {
              node [    label = "\N" ];
              London [label=London];
              Paris [label="City of\nlurve"];
              New_York [label="New York"];
              London -> Paris;
              London -> New_York [label=Far];
              Paris -> London;
          }

    as_text
        The as_text method returns text which is a layed-out dot / neato /
        twopi / circo / fdp format file.

          print $g->as_text;

          # prints out something like:
          digraph test {
              node [    label = "\N" ];
              graph [bb= "0,0,162,134"];
              London [label=London, pos="33,116", width="0.89", height="0.50"];
              Paris [label="City of\nlurve", pos="33,23", width="0.92", height="0.62"];
              New_York [label="New York", pos="123,23", width="1.08", height="0.50"];
              London -> Paris [pos="e,27,45 28,98 26,86 26,70 27,55"];
              London -> New_York [label=Far, pos="e,107,40 49,100 63,85 84,63 101,46", lp="99,72"];
              Paris -> London [pos="s,38,98 39,92 40,78 40,60 39,45"];
          }

    as_ps
        Returns a string which contains a layed-out PostScript-format file.

          print $g->as_ps;

    as_hpgl
        Returns a string which contains a layed-out HP pen plotter-format
        file.

          print $g->as_hpgl;

    as_pcl
        Returns a string which contains a layed-out Laserjet printer-format
        file.

          print $g->as_pcl;

    as_mif
        Returns a string which contains a layed-out FrameMaker
        graphics-format file.

          print $g->as_mif;

    as_pic
        Returns a string which contains a layed-out PIC-format file.

          print $g->as_pic;

    as_gd
        Returns a string which contains a layed-out GD-format file.

          print $g->as_gd;

    as_gd2
        Returns a string which contains a layed-out GD2-format file.

          print $g->as_gd2;

    as_gif
        Returns a string which contains a layed-out GIF-format file.

          print $g->as_gif;

    as_jpeg
        Returns a string which contains a layed-out JPEG-format file.

          print $g->as_jpeg;

    as_png
        Returns a string which contains a layed-out PNG-format file.

          print $g->as_png;
          $g->as_png("pretty.png"); # save image

    as_wbmp
        Returns a string which contains a layed-out Windows BMP-format file.

          print $g->as_wbmp;

    as_cmap (deprecated)
        Returns a string which contains a layed-out HTML client-side image
        map format file. Use as_cmpax instead.

          print $g->as_cmap;

    as_cmapx
        Returns a string which contains a layed-out HTML HTML/X client-side
        image map format file.

          print $g->as_cmapx;

    as_ismap (deprecated)
        Returns a string which contains a layed-out old-style server-side
        image map format file. Use as_imap instead.

          print $g->as_ismap;

    as_imap
        Returns a string which contains a layed-out HTML new-style
        server-side image map format file.

          print $g->as_imap;

    as_vrml
        Returns a string which contains a layed-out VRML-format file.

          print $g->as_vrml;

    as_vtx
        Returns a string which contains a layed-out VTX (Visual Thought)
        format file.

          print $g->as_vtx;

    as_mp
        Returns a string which contains a layed-out MetaPost-format file.

          print $g->as_mp;

    as_fig
        Returns a string which contains a layed-out FIG-format file.

          print $g->as_fig;

    as_svg
        Returns a string which contains a layed-out SVG-format file.

          print $g->as_svg;

    as_svgz
        Returns a string which contains a layed-out SVG-format file that is
        compressed.

          print $g->as_svgz;

    as_plain
        Returns a string which contains a layed-out simple-format file.

          print $g->as_plain;

NOTES
    Older versions of GraphViz used a slightly different syntax for node and
    edge adding (with hash references). The new format is slightly clearer,
    although for the moment we support both. Use the new, clear syntax,
    please.

SEE ALSO
    GraphViz::XML, GraphViz::Regex

AUTHOR
    Leon Brocard <acme@astray.com>

COPYRIGHT
    Copyright (C) 2000-4, Leon Brocard

    This module is free software; you can redistribute it or modify it under
    the same terms as Perl itself.

