# Output Formats

The output format is specified with the -Tlang flag on the command line, where lang is one of the parameters listed below.

Note that the internal coordinate system has the origin in the lower left corner. Thus, positions in the canon, dot, xdot, plain, and plain-ext formats need to be interpreted in this manner.

Command-line parameter | Format
--- | ---
canon dot xdot | DOT
cmap | Client-side imagemap (deprecated)
dia | Dia format
fig | FIG
gd gd2 | GD/GD2 formats
gif | GIF
hpgl | HP-GL/2
imap cmapx | Server-side and client-side imagemaps
ismap | Server-side imagemap (deprecated)
jpg jpeg | JPEG (deprecated - 8 May 2006 - will no longer be supported)
mif | FrameMaker MIF format
mp | MetaPost
pcl | PCL
pic | PIC
plain plain-ext | Simple text format
png | Portable Network Graphics format
ps | PostScript
ps2 | PostScript for PDF
svg svgz | Scalable Vector Graphics
vrml | VRML
vtx | Visual Thought format
wbmp | Wireless BitMap format

## Format Descriptions

canon ,
dot ,
xdot
  These formats produce output in the dot language. Using canon produces a prettyprinted version of the input, with no layout performed.

  The dot option corresponds to attributed dot output, and is the default output format. It reproduces the input, along with layout information for the graph. In particular, a bb attribute is attached to the graph, specifying the bounding box of the drawing. If the graph has a label, its position is specified by the lp attribute.

  Each node gets pos, width and height attributes. If the node is a record, the record rectangles are given in the rects attribute. If the node is a polygon and the vertices attribute is defined, this attribute contains the vertices of the node.

  Every edge is assigned a pos attribute, and if the edge has a label, the label position is given in lp.

  The xdot format extends the dot format by providing much more detailed information about how graph components are drawn. It relies on additional attributes for nodes, edges and graphs. The format is preliminary; comments and suggestions for better representations are welcome.

  At present, additional drawing attributes are only attached to nodes and edges. There are six new attributes:

  _draw_ | Drawing operations
  _ldraw_ | Label drawing
  _hdraw_ | Head arrowhead | Edge only
  _tdraw_ | Tail arrowhead | Edge only
  _hldraw_ | Head label | Edge only
  _tldraw_ | Tail label | Edge only

  The value of these attributes consists of the concatenation of some (multi-)set of the following 12 rendering or attribute operations.

  E x0 y0 w h | Filled ellipse ((x-x0)/w)2 + ((y-y0)/h)2 = 1
  e x0 y0 w h | Unfilled ellipse ((x-x0)/w)2 + ((y-y0)/h)2 = 1
  P n x1 y1 ... xn yn | Filled polygon using the given n points
  p n x1 y1 ... xn yn | Unfilled polygon using the given n points
  L n x1 y1 ... xn yn | Polyline using the given n points
  B n x1 y1 ... xn yn | B-spline using the given n control points
  b n x1 y1 ... xn yn | Filled B-spline using the given n control points
  T x y j w n -c1c2...cn | Text drawn using the baseline point (x,y). The text consists of the n characters following '-'. The text should be left-aligned (centered, right-aligned) on the point if j is -1 (0, 1), respectively. The value w gives the width of the text as computed by the library.
  C n -c1c2...cn | Set fill color. The color value consists of the n characters following '-'.
  c n -c1c2...cn | Set pen color. The color value consists of the n characters following '-'.
  F s n -c1c2...cn | Set font. The font size is s points. The font name consists of the n characters following '-'.
  S n -c1c2...cn | Set style attribute. The style value consists of the n characters following '-'. The syntax of the value is the same as specified for a styleItem in style.

  In handling alignment, the application may want to recompute the string width using its own rendering primitives.

  The text operation is only used in the label attributes. Normally, the non-text operations are only used in the non-label attributes. If, however, the decorate attribute is set on an edge, its label attribute will also contain a polyline operation. In addition, if a label is a complex, HTML-like label, it will also contain non-text operations.

  All coordinates and sizes are in points. Note though that if an edge or node is invisible, no drawing operations are attached to it.

cmap
  Produces map files for client-side image maps. The cmap format is mostly identical to cmapx, but the latter is well-formed XML amenable to processing by XML tools. In particular, the cmapx output is wrapped in <map></map>.
dia
  Produces Dia output.
fig
  Outputs graphs in the FIG graphics language.
gd ,
gd2
  Output images in the GD and GD2 format. These are the internal formats used by the gd library. The latter is compressed.
gif
  Outputs GIF bitmap images.
hpgl
  Produces output in the HP-GL/2 vector graphic printer language.
imap ,
cmapx
  Produces map files for server-side and client-side image maps, These can be used in a web page with a graphical form of the output, e.g. in JPEG or GIF format, to attach links to nodes and edges. For example, to create a server-side map given the dot file

        /* x.dot */
        digraph mainmap {
          URL="http://www.research.att.com/base.html";
          command [URL="http://www.research.att.com/command.html"];
          command -> output [URL="colors.html"];
        }

  one would process the graph and generate two output files:

        dot -Timap -ox.map -Tgif -ox.gif x.dot

  and then refer to it in a web page:

        <A HREF="x.map"><IMG SRC="x.gif" ismap="ismap" /></A>

  For client-side maps, one again generates two output files:

        dot -Tcmapx -ox.map -Tgif -ox.gif x.dot

  and uses the HTML

        <IMG SRC="x.gif" USEMAP="#mainmap" />
        ... [content of x.map] ...

  URLs can be attached to the root graph, nodes and edges. If a node has a URL, clicking in the node will activate the link. If an edge has a URL, various points along the edge (but not necessarily the head or tail) will link to it. In addition, if the edge has a label, that will link to the URL. As for the head of the edge, this is linked to the headURL, if set. Otherwise, it is linked to the edge's URL if that is defined. The analogous description holds for the tail and the tailURL. A URL associated with the graph is used as a default link.

  If the URL of a node contains the escape sequence "\N", it will be replaced by the node's name. If the headURL is defined and contains the escape sequence "\N", it will be replaced by the headlabel, if defined. The analogous result holds for the tailURL and the taillabel.

ismap
  Produces HTML image map files. This is a predecessor (circa 1994) of the IMAP format. Most servers now use the latter. URLs can be attached to the root graph, nodes and edges. Since edge links are attached to edge labels, an edge must have a label for its URL to be used. For both nodes and edges, if the URL has the escape sequence "\N" embedded in its string, this will be replaced with the node or edge name.
jpg ,
jpeg
  Output JPEG compressed image files. This format relies on the installation having the JPEG library.
mif
  Generates Frame Maker MIF files.
mp
  Produces MetaPost output.
pcl
  Produces output in the PCL printer language. HP-GL is a subset of PCL, so that PCL output is the same as HP-GL, wrapped with some initial and final commands to set the printer to and from HP-GL mode.
pic
  Outputs in PIC, the picture description language in the troff-family
plain ,
plain-ext
  The plain and plain-ext formats produce output using a simple, line-based language. The latter format differs in that, on edges, it provides port names on head and tail nodes when applicable.

  There are four types of statements.

         graph scale width height
         node name x y width height label style shape color fillcolor
         edge tail head n x1 y1 .. xn yn [label xl yl] style color
         stop

  graph
    The width and height values give the width and height of the drawing. The lower left corner of the drawing is at the origin. The scale value indicates how the drawing should be scaled if a size attribute was given and the drawing needs to be scaled to conform to that size. If no scaling is necessary, it will be set to 1.0. Note that all graph, node and edge coordinates and lengths are given unscaled.
  node
    The name value is the name of the node, and x and y give the node's position. The width and height are the width and height of the node. The label, style, shape, color and fillcolor give the node's label, style, shape, color and fillcolor, respectively, using attribute default values where necessary. If the node does not have a style attribute, "solid" is used.
  edge
    The tail and head values give the names of the head and tail nodes. In plain-ext format, the head or tail name will be appended with a colon and a portname if the edge connects to the node at a port. n is the number of control points defining the B-spline forming the edge. This is followed by 2*n numbers giving the x and y coordinates of the control points in order from tail to head. If the edge has a label, this comes next followed by the x and y coordinates of the label's position. The edge description is completed by the edge's style and color. As with nodes, if a style is not defined, "solid" is used.

    Note: The control points given in an edge statement define the body of the edge. In particular, if the edge has an arrowhead to the head or tail node, there will be a gap between the last or first control points and the boundary of the associated node. There are at least 3 possible ways of handling this gap:

    - Arrange that the input graph uses `dir=none`, `arrowhead=none`, or `arrowtail=none` for all edges. In this case, the terminating control points will always touch the node.
    - Consider the line segment joining the control point and the center of the node, and determine the point where the segment intersects the node's boundary. Then use the control point and the intersection point as the main axis of an arrowhead. The problem with this approach is that, if the edge has a port, the edge will not be pointing to the center of the node. In this case, rather than use the control point and center point, one can use the control point and its tangent.
    - Arrange that the input graph uses `headclip=false` or `tailclip=false`. In this case, the edge will terminate at the node's center rather than its boundary. If arrowheads are used, there will still be a gap, but normally this will occur within the node. The application will still need to clip the spline to the node boundary. Also, as with the previous item, if the edge points to a node port, this technique will fail.
  The output consists of one graph line, a sequence of node lines, one per node, a sequence of edge lines, one per edge, and a final stop line. All units are in inches, represented by a floating point number.

  Note that the plain formats provide minimal information, really giving not much more than node positions and sizes, and edge spline control points. These formats are usually most useful to applications wanting just this geometric information, and willing to fill in all of the graphical details. The only real advantages to these formats is their terseness and their ease of parsing. In general, the dot and xdot are preferable in terms of the quantity of information provided.

png
  Produces output in the PNG (Portable Network Graphics) format. PNG relies on having libz and the PNG library.
ps
  Produces PostScript output.
ps2
  Produces PostScript output with PDF notations. It is assumed the output will be directly converted into PDF format. The notations include PDF bounding box information, so that the resulting PDF file can be correctly used with pdf tools, such as pdflatex. In addition, if a node has a URL attribute, this gets translated into PDF code such that the node, when viewed in a PDF-viewer, e.g., acroread, is a link to the given URL. If a URL is attached to the graph, this serves as a base, such that relative URLs on nodes are derived from it.
svg ,
svgz
  Produce SVG output, the latter in compressed format. SVG relies on having libz.
vrml
  Outputs graphs in the VRML format. To get a 3D embedding, nodes must have a z attribute. These can either be supplied as part of the input graph, or be generated by neato provided dim`=3` and at least one node has a z value.

  Line segments are drawn as cylinders. In general, VRML output relies on having the PNG library to produce images used to texture-fill the node shapes. However, if shape`=point`, a node is drawn as a 3D sphere.

vtx
  Generates graph diagrams in the format for Confluents's Visual Thought.
wbmp
  Produces output in the Wireless BitMap (WBMP) format, optimized for mobile computing.