Unchained.Pptx.Rendering 0.1.0-rc.4

Unchained.Pptx.Rendering

Slide rasterization for Unchained.Pptx. Renders PPTX slides to PNG (or other image formats) using FreeType2 for font rasterization and HarfBuzz for text shaping.

Installation

<PackageReference Include="Unchained.Pptx.Rendering" />

The FreeType2 native library is supplied automatically — by the FreeTypeSharp package on Windows, macOS, and linux-x64, and by Unchained.Drawing.Runtimes on linux-arm64. No manual fetch step is needed to consume the package.

Building the repo from source on linux-arm64 is the one case that needs a fetch (the binary is not committed):

# linux-arm64 host only — every other platform is a no-op
bash scripts/FetchNatives/fetch-natives.sh --rid linux-arm64

Quick start

using Unchained.Pptx.Engine;
using Unchained.Pptx.Rendering;
using Unchained.Pptx.Rendering.Engine;

var processor = new PresentationProcessor();
var doc = await processor.LoadAsync("presentation.pptx");

// Render all slides at 1920×1080 (default)
var images = await SlideRenderer.RenderAllAsync(doc);

// Save each slide as PNG
for (var i = 0; i < images.Length; i++)
    await images[i].SaveAsync($"slide{i + 1}.png");

// Render a single slide at custom resolution
var thumbnail = await SlideRenderer.RenderAsync(
    doc.Slides[0],
    doc.SlideSize,
    new RenderOptions { WidthPx = 640, HeightPx = 360 },
    doc.Media); // pass Media so embedded fonts are used

Pass document.Media to RenderAsync (it is passed automatically by RenderAllAsync) so embedded fonts resolve. Without it, custom typefaces fall back to bundled substitutes.

Fonts

Runs are rendered with FreeType2 + HarfBuzz. Font resolution order per run:

1. Embedded font — if the presentation embeds the run's typeface (<p:embeddedFontLst> → /ppt/fonts/*.fntdata), the real font bytes are used, matched by typeface and style (regular/bold/italic/bold-italic).
2. Bundled substitute — Standard-14 names map to DejaVu; everything else falls back to NotoSans-Regular.

Glyphs are blitted via BlitGlyphFromFace, which reads the FreeType glyph slot through FreeTypeSharp's typed structs. Marshaling is correct on every platform — including Windows x64, where the previous SharpFont binding used a wrong Face.Glyph offset and yielded empty bitmaps (the old cause of missing text in slide renders).

Output formats

RenderOptions.Format selects the encoder:

The returned PptxImage.Format always matches the bytes in PptxImage.Data.

Embedded images

Embedded PNG pictures (p:pic) are decoded (BCL-only inflate + unfiltering) and blitted into their shape rectangle. Other formats — JPEG, EMF/WMF, SVG, WDP — are not yet decoded; those picture regions are left transparent. Text, shapes, and solid fills always render.

Dependencies

Bundled fonts: DejaVu (Bitstream Vera / SIL OFL) · NotoSans-Regular (SIL OFL)

Targets

net8.0 · net9.0 · net10.0

License

MIT — no commercial restrictions.