PostScript is a specialised page description language developed by Adobe Systems and first introduced in 1982, designed to provide a precise, device independent means of describing the appearance of text, graphics, and images on a printed page in a way that can be interpreted and reproduced accurately by any PostScript compatible output device regardless of its specific resolution, paper size, or hardware characteristics. It was one of the foundational technologies of the desktop publishing revolution of the 1980s, enabling for the first time the production of high quality, professionally typeset documents and graphics from desktop computers connected to laser printers and high resolution imagesetters.
PostScript operates as a complete programming language rather than simply a data format, describing the content and appearance of a page through a series of mathematical instructions and geometric descriptions that define the precise shapes, positions, sizes, and relationships of all the elements on the page. Text characters are described as mathematical outlines - Bézier curves defining the precise contour of each letterform - rather than as fixed bitmap patterns of dots, allowing them to be rendered at any size and at any resolution the output device is capable of producing, with smooth, accurate edges and consistent appearance regardless of scale. Similarly, graphic elements including lines, shapes, fills, and gradients are described geometrically, allowing them to be rendered at the full resolution of the output device without the jagged, pixelated appearance that would result from scaling a fixed resolution bitmap image.
In the context of photographic and imaging workflows, PostScript is of fundamental importance as the page description language underlying the majority of professional quality laser printers, high resolution imagesetters, and digital printing systems used in commercial print production. When a photographer or designer sends an image or layout to a PostScript printer, the host application - whether Adobe Photoshop, InDesign, Illustrator, or any other PostScript aware application - generates a PostScript description of the page that encodes the image data, colour profile information, layout geometry, and all other page elements in PostScript language. The PostScript interpreter built into the printer - or a separate raster image processor device connected between the computer and the printer - receives this PostScript description, interprets the instructions, and renders the complete page as a high resolution bitmap at the printer's native resolution before transferring it to the print engine for physical output.
PostScript's device independence - the ability of a PostScript description to be rendered correctly on any PostScript output device regardless of its resolution or capabilities - was a transformative advantage in professional print production, as it allowed the same document to be output at low resolution on a desktop laser printer for proofing and review, and then at high resolution on a commercial imagesetter for final film or plate output, with the assurance that the two outputs would be visually consistent in appearance despite their very different resolutions. This workflow of low resolution desktop proofing followed by high resolution commercial output became the standard practice of the professional publishing and print production industry throughout the late 1980s and 1990s.
PostScript Level 2, introduced in 1991, extended the original language with improved colour handling, better compression, and enhanced imaging capabilities. PostScript 3, introduced in 1997, added support for smooth shading, improved colour management, and a wider range of image compression options suited to the demands of high quality colour printing and web offset reproduction. The PostScript language and its associated technologies continue to underpin a substantial proportion of professional print production workflows, though the PDF format - itself derived from PostScript and developed by Adobe as a more compact and self-contained document format - has become the dominant file format for the exchange and delivery of print ready documents in most contemporary professional workflows.