Customizing document styles with FSharp.Markdown.Pdf

Following on from my last post on formatting a Markdown document into PDF using FSharp.Markdown.Pdf, if you don’t like the default styling (which I tried to mimic style Github formats Markdown documents with) you can set your own styling for the different types of Markdown elements by going down a level of abstraction.

The FSharp.Markdown.Pdf.MarkdownStyleNames module defines all the names of styles used to format the different Markdown elements (e.g. heading 1-6, code block, listing 1-3, etc.) into PDF. To override the default styles, you need to:

  1. Instantiate an instance of the Document type from the MigraDoc.DocumentObjectModel namespace.
  2. Add the predefined style names from the aforementioned MarkdownStyleNames module to the document’s collection of styles.
  3. Tweak the style to your liking.
  4. Call the FSharp.Markdown.Pdf.PdfFormatting.formatMarkdown function with the Document value.
  5. Voila! You now have an instance of PdfDocument which has been formatted with your custom styling.

to see these simple steps in action:

You can compare the original and customized PDF outputs here and here.

F# – PDF fun with Markdown and FSharp.Formatting

I spent the last couple of nights putting together a simple Markdown to PDF formatter using Tomas Petricek’s FSharp.Formatting project and the PdfSharp-MigraDoc library.

To use this library, you can either grab the source from the GitHub repository or get it from Nuget using the following command:

NuGet package

F# Usage

To use the library from F#, you can use the Markdown type defined in the FSharp.Markdown namespace (from the FSharp.Formating library), once you’ve opened the FSharp.Markdown.Pdf namespace you’ll have access to two static extension methods:

  • TransformPdf – accepts a string as input and outputs the resulting PDF to a local file path or to a specified Stream.
  • WritePdf – accepts a MarkdownDocument generated by the Markdown.Parse method, and outputs the resulting PDF to a local file path or to a specified Stream.

C# Usage

You can also use this library from C#, however, the static extension methods mentioned above is not accessible in C# because type extensions defined in F# are compiled differently to standard extension methods you find in C# (with far more possibilities I might add, such as extension properties, and static methods, for instance!) and is not recognized by the C# compiler..

You can still access the same functionalities using a MarkdownPdf type, with two static methods:

  • Transform – equivalent to Markdown.TransformPdf.
  • Write – equivalent to Markdown.WritePdf.

You can see an example output here with the corresponding Markdown here.