PostScript

PostScript, short for Adobe PostScript, is a page description language created by John Warnock and Charles Geschke at Adobe Systems in 1982. It is primarily used for desktop publishing, vector graphics, printing, and document layout in printers, typesetting systems, and graphics software. Developers and designers can use PostScript by installing compatible printers or software such as Ghostscript, which provides interpreters, converters, and tools for Windows, macOS, and Linux.

PostScript exists to provide a device-independent language for describing the layout and graphical content of printed pages. Its design philosophy emphasizes precision, scalability, and programmability. By representing text, vector shapes, and raster images as instructions, PostScript solves the problem of consistent high-quality output across diverse printing devices and typesetting systems.

PostScript: Basic Drawing

PostScript provides primitives for defining paths, shapes, and text on a page.

%!PS
/newpath
100 100 moveto
200 200 lineto
stroke
showpage

The moveto and lineto operators create paths, and stroke renders them. showpage outputs the page. This vector-based approach is analogous to path drawing in SVG and procedural graphics in Processing.

PostScript: Variables and Procedures

PostScript allows variables and procedures to modularize code.

/circle { % x y r
    newpath
    0 360 arc
    stroke
} def

100 100 50 circle

Procedures defined with def encapsulate reusable drawing routines. Variables and stack manipulation provide procedural control, similar to defining functions in Lisp or Forth, both of which influenced PostScript's design.

PostScript: Text and Fonts

PostScript supports detailed typographic control, including font selection and text placement.

/Times-Roman findfont
24 scalefont
setfont
100 200 moveto
(Hello, PostScript!) show
showpage

Fonts are selected and scaled, then text is positioned using moveto. This allows precise control over layout, similar to typesetting commands in TeX or vector layout in SVG.

PostScript: Loops and Arithmetic

PostScript includes operators for arithmetic and iteration, enabling programmatic page generation.

0 1 4 { % i from 0 to 4
    100 exch 100 mul moveto
    50 50 0 360 arc
    stroke
} for
showpage

The for loop iterates over values on the stack. Arithmetic operations and looping allow complex graphics to be generated algorithmically, similar to loops in Processing or stack-based languages like Forth.

PostScript: Color and Graphics State

PostScript manages color, line styles, and graphics state for advanced rendering.

0.5 0.2 0.8 setrgbcolor
newpath
100 100 moveto
200 100 lineto
200 200 lineto
100 200 lineto
closepath
fill
showpage

Setting the RGB color and defining paths allows colored shapes. The graphics state controls fill, stroke, and transformations. This enables consistent, repeatable output across devices, analogous to color management in SVG or Processing.

Overall, PostScript provides a precise, programmable, and device-independent environment for page description and vector graphics. When used with SVG, Processing, and Forth, it allows developers and designers to produce complex graphical layouts, typographic designs, and print-ready content efficiently. Its stack-based language, procedural capabilities, and robust graphics primitives make PostScript a durable and foundational tool in digital publishing and graphics.