Package: pelican-graphviz
Graphviz: A Plugin for PelicanGraphviz is a Pelican plugin that allows the inclusion ofGraphvizimages using the Markdown markup format. The code for the Graphviz figure is included as a block in the article’s source, and the image is embedded in HTML using the Base64 format.InstallationThis plugin can be installed via:python -m pip install pelican-graphvizGraphviz must be installed on the system, otherwise this plugin will be deactivated. Graphviz can be installed on Debian-based systems via:sudo aptitude install graphvizFor macOS, Graphviz can be installed via Homebrew:brew install graphvizUsageIn the Markdown source, the Graphviz code must be inserted as an individual block (i.e., separated from the rest of the material by blank lines), like the following:..graphviz dot
digraph G {
  graph [rankdir = LR];
  Hello -> World
}This will insert an image in your article like this:The block must start with..graphviz(this is configurable — see below). The worddotin the first line indicates the program that will be run to produce the image. The available programs are:dot,neato,twopi,circo,fdp,sfdp, andpatchwork(see theGraphviz documentationfor details). The Graphviz code must start in the second line of the block. Notice thatnewlines are not allowed inside the Graphviz block.Styling with CSSThe image is generated in HTML with an<img>element inside an HTML element (by default a<div>, but this is configurable — see below). The latter has classgraphviz(this is also configurable — see below). A possible CSS styling would be:div.graphviz{margin:10px;}div.graphvizimg{display:block;padding:5px;margin-left:auto;margin-right:auto;text-align:center;border-style:solid;border-width:1px;border-color:rgb(192,177,177);-webkit-border-radius:5px;}ConfigurationThe following variables can be set in the Pelican settings file:GRAPHVIZ_HTML_ELEMENT: The HTML inside which the generated Graphviz image is inserted (defaults to'div'; another sensible possibility would be'span').GRAPHVIZ_IMAGE_CLASS: Class of the<div>element including the generated Graphviz image (defaults to'graphviz').GRAPHVIZ_BLOCK_START: Starting tag for the Graphviz block in Markdown (defaults to'..graphviz').GRAPHVIZ_COMPRESS: Compress the resulting SVG XML to an image (defaults toTrue). Without compression, more SVG features are available, for instance including clickable URLs inside the Graphviz diagram.The values above can be overridden for each individual block using the syntax below:..graphviz [key=val, ...] dotThe allowed keys arehtml-element,image-class, andcompress. For the latter, the value can be eitheryesorno.Output Image FormatThe format of the embedded image is SVG, and there is currently no way to change it. This format was chosen over others (like PNG) for two reasons. First, the generated SRC string in Base64 seem to be shorter for SVG than for PNG. Second, the image will be available in the browser in a high-quality vectorized format. As a caveat, notice that this choice may prevent display in browsers lacking proper SVG support.AlternativesAn alternative to this plugin is theGraphviz tagprovided by theLiquid Tags plugin, which differs from this plugin in several respects. First, the Liquid Tags version uses the syntax{% graphviz { <program> […] } %}, while this Graphviz plugin uses the Markdown extension syntax..graphviz <program> […]. Regarding the rendered output, the differences are:Both plugins output an element withclass="graphviz". However, only the Graphviz plugin allows you to change the class name via a configuration variable (GRAPHVIZ_IMAGE_CLASS).Liquid Tags encodes the image assrc="data:image/png;base64,[…]", while the Graphviz plugin encodes it assrc="data:image/svg+xml;base64,[…]". This has two impacts. First, the size of the HTML code produced by this Graphviz plugin is much smaller. For example, the Base64 string for the Graphviz codedigraph graphname {a -> b -> c; b -> d;}is four times smaller. Second, the Liquid Tags version generates a raster image file, whereas this Graphviz plugin produces a vector image that can be zoomed without image quality loss.Liquid Tags outputs the Graphviz image inside a<span>, whereas this Graphviz plugin offers a choice for the container element.To-DoContributions that make this plugin work withreStructuredTextcontent are welcome.ContributingContributions are welcome and much appreciated. Every little bit helps. You can contribute by improving the documentation, adding missing features, and fixing bugs. You can also help out by reviewing and commenting onexisting issues.To start contributing to this plugin, review theContributing to Pelicandocumentation, beginning with theContributing Codesection.AcknowledgmentsThanks toJustin Mayer, for helping with migration of this plugin under the Pelican Plugins organization, and toMaxim Kochurov, for introducing theGRAPHVIZ_COMPRESSconfiguration variable.AuthorCopyright © 2015, 2021, 2023  Rafael Laboissièrerafael@laboissiere.netLicenseThis project is licensed under the terms of the AGPL 3.0 license.