Postscript

Pure-Ruby PostScript (PS) / EPS parser, typed domain model, and serializer. The lower layer of the postsvg converter. Independently reusable for any tool that needs to read, write, or transform PostScript source.

Installation

gem install postscript

Usage

require "postscript"

# Parse PS source into a typed AST
program = Postscript::Source.parse(<<~PS)
  %!PS-Adobe-3.0 EPSF-3.0
  %%BoundingBox: 0 0 100 100
  newpath
  10 10 moveto
  90 10 lineto
  90 90 lineto
  10 90 lineto
  closepath
  fill
  showpage
PS

# Walk the AST
program.body.each do |node|
  puts node.class
end

# Re-serialize back to PS source
ps_text = Postscript::Serializer.call(program)
puts ps_text

Architecture

Three layers, each with a single responsibility:

Layer	Owns
`Postscript::Source`	PS source → tokens → `Model::Program`. Lexer is comment-aware.
`Postscript::Model`	Typed PS records: `Program`, `Literals::`, `Operators::` (one class per PS operator).
`Postscript::Serializer`	`Model::Program` → PS source text.

Adding a new PS operator = writing one subclass + one visit_* method. No switch edits (OCP).

Value types

This gem also hosts three general-purpose value types that postsvg depends on:

Postscript::Matrix — 2D affine transform.
Postscript::Color — RGB / Gray / CMYK immutable value.
Postscript::FormatNumber — float → PS-safe text.

License

BSD-2-Clause. See LICENSE.