FOP.Sharp 26.6.2312

Apache FOP for .NET

A modern, cross-platform C# port of Apache FOP (Formatting Objects Processor): read an XSL-FO document and render it to PDF, plain text, Markdown or HTML. It targets .NET 10, runs anywhere .NET runs (Windows, Linux, macOS), and replaces FOP's Java AWT/Java2D/Batik stack with managed libraries (PdfSharp, SixLabors.ImageSharp, SixLabors.Fonts).

This is the C# port. The original Java sources live alongside it in this repository (fop-core/, fop-util/, fop/, …) and remain the source of truth for the port; see the upstream Apache FOP README for the Java project. The .NET solution lives under dotnet/.

Packages

The port is split into many small component projects internally, but ships as two NuGet packages:

What's inside the FOP.Sharp package

The FOP.Sharp library package is self-contained: it bundles every component assembly of the port (you only ever reference FOP.Sharp). The bundled assemblies are:

Its third-party NuGet dependencies (PdfSharp, SixLabors.ImageSharp, SixLabors.Fonts, SixLabors.ImageSharp.Drawing) are declared on the package and restored automatically.

Installation

# Library
dotnet add package FOP.Sharp

# Command-line tool (global)
dotnet tool install --global FOP.Sharp.Cli

Usage

Render XSL-FO to PDF (library)

using Fop.Render.Pdf;

var processor = new FopProcessor();

// From a file
processor.ConvertFile("input.fo", "output.pdf");

// From a string, into a byte[]
byte[] pdf = processor.Convert(File.ReadAllText("input.fo"));

// From streams
using var fo  = File.OpenRead("input.fo");
using var pdf2 = File.Create("output.pdf");
processor.Convert(fo, pdf2);

Register custom fonts before converting (Liberation faces are bundled as the fallback):

var processor = new FopProcessor();
processor.RegisterFont("MyFont-Regular.ttf", "My Font");
processor.RegisterFontsDirectory("./fonts");
processor.ConvertFile("input.fo", "output.pdf");

Use the native, PdfSharp-free renderer (supports font subsetting and encryption):

byte[] pdf = processor.ConvertNative(File.ReadAllText("input.fo"));

Render to plain text, Markdown or HTML (library)

using Fop.Render.Text;

string text     = new PlainTextRenderer().Convert(foXml);
string markdown = new MarkdownRenderer().Convert(foXml);
string html     = new HtmlRenderer().Convert(foXml);

Command-line tool

# Output format inferred from the extension
fop input.fo output.pdf
fop input.fo output.md

# Explicit flags
fop -fo input.fo -pdf output.pdf
fop -xml data.xml -xsl style.xsl -html output.html

# Register fonts / use the native renderer
fop -fo input.fo -pdf out.pdf -fontdir ./fonts -native

Run fop -help for the full option list.

Building from source

cd dotnet
dotnet build Fop.slnx
dotnet test  Fop.slnx

Requires the .NET 10 SDK (pinned in dotnet/global.json).

To produce the NuGet packages locally:

cd dotnet
dotnet pack src/Fop/Fop.csproj         -c Release   # the Fop library
dotnet pack src/Fop.Cli/Fop.Cli.csproj -c Release   # the fop .NET tool

Status

The port is an incremental, bottom-up effort. A working end-to-end FO → PDF pipeline already covers a substantial XSL-FO subset (block/inline text, fonts, colour, the box model, tables, lists, static content, keeps & breaks, footnotes, floats, markers, links, leaders, hyphenation, Knuth–Plass line breaking, embedded SVG, bookmarks and more). See dotnet/CLAUDE.md for the architecture and dotnet/TODO.md for the phased plan and current progress.

License

Licensed under the Apache License, Version 2.0, the same license as upstream Apache FOP.