PGF

PGF, or Portable Graphics Format, is a free and open-source TeX macro package for generating graphics within LaTeX documents. It provides low-level drawing primitives and a compact macro language to create paths, coordinates, colors, and decorations. PGF is engine-agnostic and works with pdfLaTeX, XeLaTeX, and LuaLaTeX. It forms the core of the PGF/TikZ package, with TikZ offering a higher-level, user-friendly interface built on top of PGF.

History and scope: Developed by Till Tantau in the 1990s, PGF has become a widely used tool for programmatic graphics in LaTeX. The project is open source and maintained by a community of contributors. It provides libraries for shapes, plots, shading, arrows, and 3D drawing, enabling complex illustrations without external graphics software.

Features: The language is path-based and coordinate-driven, supporting Cartesian, polar, and custom coordinate systems, transformations, layering, and scopes. It includes libraries for decorations, patterns, and plots; supports color management, transparency, and font consistency with TeX. It can output to PDF-friendly primitives and integrates with external plotting tools such as pgfplots.

Usage: PGF is typically used through TikZ, which provides a more natural syntax for diagrams and graphics. It is also possible to use PGF directly for low-level tasks. The combination with pgfplots offers high-quality mathematical plots. It is widely supported by TeX editors and compilers and yields vector graphics that scale with document fonts.

Availability and license: PGF/TikZ is free and open-source and distributed with major TeX distributions such as TeX Live and MiKTeX. It is actively developed and documented, with extensive online resources and a large user community.