PostForge – A PostScript interpreter written in Python

Hi HN, I built a PostScript interpreter from scratch in Python.

PostForge implements the full PostScript Level 2 specification — operators, graphics model, font system, save/restore VM, the works. It reads .ps and .eps files and outputs PNG, PDF, SVG, or renders to an interactive Qt window.

Why build this? GhostScript is the only real game in town for PostScript interpretation, and it's a 35-year-old C codebase. I wanted something where you could actually read the code, step through execution, and understand what's happening. PostForge is modular and approachable — each operator category lives in its own file, the type system is clean, and there's an interactive prompt where you can poke at the interpreter state.

Some technical highlights:

- Full Level 2 compliance with selected Level 3 features - PDF output with Type 1 font reconstruction/subsetting and TrueType/CID embedding - ICC color management (sRGB, CMYK, Gray profiles via lcms2) - Optional Cython-compiled execution loop (15-40% speedup) - 2,500+ unit tests written in PostScript itself using a custom assertion framework - Interactive executive mode with live Qt display — useful for debugging PS programs

What it's not: A GhostScript replacement for production/printer use. It's interpreted Python, so it's slower. But it handles complex real-world PostScript files well and the output quality is solid.

I'd love feedback, especially from anyone who's worked with PostScript or built language interpreters. The architecture docs are at docs/developer/architecture-overview.md if you want to dig in.