fop-render

Rendering backends for the Apache FOP Rust implementation. Transforms the area tree (from fop-layout) into output formats. Currently supports PDF output.

Usage

use fop_core::FoTreeBuilder;
use fop_layout::LayoutEngine;
use fop_render::PdfRenderer;
use std::io::Cursor;

let xml = r#"<?xml version="1.0"?>
<fo:root xmlns:fo="http://www.w3.org/1999/XSL/Format">
    <fo:layout-master-set>
        <fo:simple-page-master master-name="A4"
            page-width="210mm" page-height="297mm">
            <fo:region-body margin="1in"/>
        </fo:simple-page-master>
    </fo:layout-master-set>
    <fo:page-sequence master-reference="A4">
        <fo:flow flow-name="xsl-region-body">
            <fo:block font-size="14pt">Hello, PDF!</fo:block>
        </fo:flow>
    </fo:page-sequence>
</fo:root>"#;

let fo_tree = FoTreeBuilder::new().parse(Cursor::new(xml)).unwrap();
let area_tree = LayoutEngine::new().layout(&fo_tree).unwrap();

let renderer = PdfRenderer::new();
let pdf_doc = renderer.render(&area_tree).unwrap();
let bytes = pdf_doc.to_bytes().unwrap();

std::fs::write("output.pdf", &bytes).unwrap();

Architecture

`pdf/` - PDF Backend

File	Lines	Description
`document.rs`	286	`PdfDocument` - PDF object model (pages, fonts, catalog)
`writer.rs`	154	`PdfRenderer` - area tree to PDF conversion
`graphics.rs`	291	`PdfGraphics` - PDF content stream operations

PdfDocument

Manages the PDF object graph: catalog, page tree, pages, font dictionaries, and cross-reference table. Serializes to valid PDF 1.4 bytes.

PdfRenderer

Walks the area tree and emits PDF operations for each area. Handles text rendering with font selection, color setting, and coordinate transformation (PDF uses bottom-left origin vs FOP's top-left).

PdfGraphics

Low-level PDF content stream builder. Supports:

Text operations: BT/ET, Tf, Td, Tj
Graphics state: q/Q, cm
Path operations: m, l, re, S, f
Color: rg/RG (RGB), g/G (grayscale)
Line width: w

`image.rs` - Image Support

File	Lines	Description
`image.rs`	304	`ImageFormat`, `ImageInfo`, `ImagePlacement`

Handles image format detection (PNG, JPEG, GIF, TIFF, SVG, BMP), dimension extraction from file headers, and aspect-ratio-preserving placement calculation.

Total: 1,056 lines across 5 files

Generated PDF Structure

%PDF-1.4
1 0 obj  << /Type /Catalog /Pages 2 0 R >>
2 0 obj  << /Type /Pages /Kids [...] /Count N >>
3 0 obj  << /Type /Font /Subtype /Type1 /BaseFont /Helvetica >>
4 0 obj  << /Type /Page /Parent 2 0 R /Contents 5 0 R >>
5 0 obj  << /Length ... >> stream ... endstream
...
xref
trailer
%%EOF

Tests

23 unit tests covering:

PDF document structure (catalog, page tree)
PDF serialization and cross-reference table
Text rendering with font selection
Graphics operations (lines, rectangles, colors)
Image format detection (PNG, JPEG, GIF, TIFF, SVG, BMP)
Image dimension extraction from file headers
Aspect ratio calculation and placement

Dependencies

fop-types (internal)
fop-layout (internal)
thiserror 2.0
log 0.4

fop-render 0.1.0