Johannes Thorn Ralf D. Müller Ralf D. Müller Jody Winter Jeremie Bresson Jan Hendriks Alexander Schwartz Dr. Stefan Pfeiffer Lars Francke David M. Carr

3 minutes to read

About This Task

This is the standard Asciidoctor generator which is supported out of the box. The result is written to build/html5 (the HTML files need the images folder to be in the same directory to display correctly).

Generating Single-File HTML Output

If you would like the generator to produce a single-file HTML, you can configure Asciidoctor to store the images inline as data-uri by setting :data-uri: in the config of your AsciiDoc file. But be warned. The file can quickly become very large and some browsers might struggle to render it.

Creating Text-Based Diagrams

docToolchain is configured to use the asciidoctor-diagram plugin to create PlantUML diagrams. The plugin also supports many other text-based diagrams, but PlantUML is the most common. To use the plugin, specify your PlantUML code like this:

.example diagram
[plantuml, "{plantUMLDir}demoPlantUML", png] # (1)
class BlockProcessor
class DiagramBlock
class DitaaBlock
class PlantUmlBlock

BlockProcessor <|-- DiagramBlock
DiagramBlock <|-- DitaaBlock
DiagramBlock <|-- PlantUmlBlock
  1. The element of this list specifies the diagram tool plantuml to be used. The second element is the name of the image to be created, and the third specifies the image type.

{plantUMLDir} ensures that PlantUML also works for the generatePDF task. Without it, generateHTML works fine, but the PDF will not contain the generated images.
Be sure to specify a unique image name for each diagram, otherwise they will overwrite each other.

The above example renders as:

Figure 1. example diagram

Controlling Diagram Size

If you want to control the size of the diagram in the output, configure the "width" attribute (in pixels) or the "scale" attribute (floating point ratio) passed to asciidoctor-diagram. The following example updates the diagram above by changing the declaration to one of the versions below:

[plantuml, target="{plantUMLDir}demoPlantUMLWidth", format=png, width=250]
# rest of the diagram definition

[plantuml, target="{plantUMLDir}demoPlantUMLScale", format=png, scale=0.75]
# rest of the diagram definition

The output will render like this:

Figure 2. example diagram (with specified width)
Figure 3. example diagram (with specified scale)
To work correctly, PlantUML needs Graphviz dot installed. If you can’t install it, use the Java-based version of the dot library instead. Just add !pragma layout smetana as the first line of your diagram definition.

Further Reading and Resources


Show source code of scripts/AsciiDocBasics.gradle or go directly to GitHub · docToolchain/scripts/AsciiDocBasics.gradle.
task generateHTML (
        type: AsciidoctorTask,
        group: 'docToolchain',
        description: 'use html5 as asciidoc backend') {
        attributes (
            'plantUMLDir'         : file("${docDir}/${config.outputPath}/html5").toURI().relativize(new File("${docDir}/${config.outputPath}/html5/plantUML/").toURI()).getPath(),

    // specify output folder explicitly to avoid cleaning targetDir from other generated content
    outputDir = file(targetDir + '/html5/')

    outputOptions {
        separateOutputDirs = false
        backends = ['html5']

    def sourceFilesHTML = findSourceFilesByType(['html'])
//    onlyIf {
//        sourceFilesHTML
//    }

    sources {
        sourceFilesHTML.each {
            include it.file

            File useFile = new File(srcDir, it.file)
            if (!useFile.exists()) {
                throw new Exception ("""
                The file $useFile in HTML config does not exist!
                Please check the configuration 'inputFiles' in $mainConfigFile.""")
    resources {
        config.imageDirs.each { imageDir ->
            from(new File(file(srcDir),imageDir))
   ('imageDir: '+imageDir)
            into './images'
        config.resourceDirs.each { resource ->
            from(new File(file(srcDir),resource.source))
   ('resource: '+resource.source)

    doFirst {
        if (sourceFilesHTML.size()==0) {
            throw new Exception ("""
            >> No source files defined for type 'html'.
            >> Please specify at least one inputFile in your docToolchainConfig.groovy