wghostscript

Ghostscript compiled to WebAssembly for browsers, with broad PDF/PostScript feature support and three API layers (gsapi_* C bindings, CLI, and a high-level functional TypeScript API).

Try it in the browser: ghostscript.wasmedia.org, with PDF rendering, compression, PDF/A and PDF/X conversion, text extraction and PostScript → PDF, all client-side in a Web Worker.

This is the sibling of wimagemagick — the two projects deliberately do not overlap: wimagemagick excludes Ghostscript-based features (PDF rendering), and wghostscript covers them.

Install

npm install @wasmedia/wghostscript

import { initWGhostscript } from "@wasmedia/wghostscript";

const gs = await initWGhostscript();
const pages = await gs.ops.renderPdf(pdfBytes, { dpi: 150 }); // Map of PNGs
const text = await gs.ops.extractText(pdfBytes);

Full API: docs/api.md. Works in Node, in plain browser ES modules and workers, and with bundlers; Vite's dev server, Vite module workers and webpack need a line or two of config, see Using a bundler.

Status

Pre-1.0 and working: Ghostscript (current stable, tracked automatically) compiled to WASM, with the three API layers, a Web Worker entry, and a test suite covering the py-pdf sample corpus and veraPDF-validated PDF/A output. See briefs/INITIAL.md for the design brief.

Feature scope

Included

• PDF → image rendering (rasterizing PDF pages to PNG, JPEG, TIFF, etc.)
• PDF transformation (compression, flattening, PDF/A and PDF/X conversion, merging, splitting)
• PostScript interpretation (rendering .ps input)
• Font handling / text extraction

Excluded

• Printer / CUPS output devices (not meaningful in a browser)
• X11 / GTK display devices
• Network / HTTP fetching from inside Ghostscript (security)
• Tesseract OCR integration (compose with a separate WASM OCR build instead)
• Multi-threading (single-threaded only — no SharedArrayBuffer / COOP/COEP requirement)

Technical requirements

• Ghostscript version: Always target the current stable release. CI automation polls the official Artifex mirror (ArtifexSoftware/ghostpdl-downloads) GitHub Releases API and triggers a build when a new stable tag appears.
• Scope: Ghostscript only (PostScript + PDF interpreter), not full GhostPDL (no PCL/XPS).
• API surface (three layers):
  1. Low-level gsapi_* C bindings via cwrap/ccall.
  2. CLI-style interface via callMain() (["-sDEVICE=png16m", "-o", "out.png", "input.pdf"]).
  3. High-level functional TypeScript API: renderPdf, compressPdf, extractText, psToPdf, convertPdf, etc.
• Toolchain: Emscripten inside Docker.
• Output: Single .wasm + JS glue bundle, plus an npm-distributable package (@wasmedia/wghostscript).
• File I/O: Both Emscripten MEMFS and direct ArrayBuffer/Blob passing.
• Web Workers: Supported (and recommended for non-trivial work).
• Browser support: Chrome and Safari at minimum.
• Build: Single-threaded + SIMD — works on any site without special headers.
• Fonts: URW base 35 fonts are compiled into the WASM (Ghostscript's %rom% file system), so standard fonts work offline with no setup.

Delegate libraries

The libraries Ghostscript bundles in its source tree, compiled in with it:

• libjpeg (IJG) — JPEG output and DCT streams in PDFs
• libpng — PNG output
• libtiff — TIFF output
• zlib — Flate streams in PDFs
• OpenJPEG — JPEG 2000 streams in PDFs
• jbig2dec — JBIG2 streams in PDFs
• lcms2mt — colour management / ICC profiles
• FreeType — font rendering

libidn, libpaper, IJS, CUPS and Tesseract are turned off (native/scripts/build-ghostscript.sh).

Architecture

Two layers, mirroring wimagemagick:

1. native/ — C/WASM compilation. Cross-compiles Ghostscript and delegate libraries to WASM via Emscripten inside Docker. Output: dist/wghostscript.{js,wasm}.
2. src/ — TypeScript wrapper:
   • loader.ts — initWGhostscript(), loads the WASM module
   • api.ts — gsapi_* bindings via cwrap/ccall
   • cli.ts — CLI-style execute() via callMain()
   • operations.ts — high-level functional API (renderPdf, compressPdf, extractText, psToPdf, convertPdf)
   • filesystem.ts — MEMFS + ArrayBuffer/Blob helpers
   • worker.ts — Web Worker entry point
   • types.ts — shared types
   • index.ts — public re-exports

Prior art

| Project | Status | Notes | |---------|--------|-------| | @okathira/ghostpdl-wasm | Active (v1.1.0, Nov 2025) | Most credible reference build; minimal delegate set (BMP/JPEG/PNG/PS/TIFF only); CLI-via-callMain | | @jspawn/ghostscript-wasm | Stale (last release 2022) | Basic npm package | | ochachacha/ps-wasm | Active | Browser-extension-style; PostScript viewing focus | | laurentmmeyer/ghostscript-pdf-compress.wasm | Demo | PDF compression demo (Web Worker example) |

Gaps wghostscript fills:

• Three API layers (gsapi_* + CLI + high-level functional TS API). Existing options stop at CLI-via-callMain.
• Maximum practical delegate set with color management and JPEG2000.
• Documented SIMD build.
• TypeScript-first wrapper layer.

Build & test

See docs/building.md once it lands. Short version:

npm run build           # native WASM (Docker) + TypeScript
npm run build:native    # WASM only
npm run build:ts        # TypeScript only
npm test
npm run test:watch
npm run test:browser    # headless Chrome end-to-end test of the playground
npm run playground      # local dev server hosting examples/browser

License

AGPL-3.0-or-later, matching upstream Ghostscript. Downstream users accept the copyleft obligations: any application using this package over a network must release its source under AGPL.