Tuesday, November 23, 2010

Postscript (PS) And Ghostscript

Created by John Warnock and Charles Geschke, PostScript is a concatenative programming language and is best known for its use as a page description language. Developed by Adobe Systems, it is used by publishers, print service providers, government agencies and corporations around the world. Primarily developed for printing documents on laser printers, it is a complete programming language that goes beyond the typical printer control language and can be interpreted by any printer. PostScript can be adapted to any printer even if it does not support this language. You simply need to purchase a cartridge that contains PostScript.

It is an object-oriented language that does not treat images and fonts as bit maps but as a collection of geometrical objects. The printers with PostScript can produce a multitude of fonts and print visually rich documents. There are three versions of PostScript: PostScript Level 1, PostScript Level 2 and PostScript 3. Level 1 appeared in the market in 1984, Level 2 in 1992 and PostScript 3 was released in 1997.

Level 1 was the first or basic version of the PostScript language while Level 2 was introduced with improved speed and reliability. It supports composite fonts, in-RIP separations and image decompression. It also supports the form mechanism for caching reusable memory. The latest version includes several great features and supports more fonts and handles graphics in a better way. It has replaced the existing proprietary color electronic prepress system and introduced smooth shading operations with up to 4096 shades of Grey. It allows addition of spot colors in composite color pages and is widely used for magazine production.


GhostScript is a set of software that is used as an interpreter of the PostScript language. It can also interpret Portable Document Format files and can covert them into PostScript language files, and vice-versa. This package of software has an ability to convert PostScript language files to several other formats and print on many printers without built-in PostScript language capability. Written entirely in C language, it can run properly on a wide variety of systems including Apple MacOS, MS Windows, VMS systems and UNIX and UNIX-like platforms.

A full set of Type 1 fonts is supplied for GhostScript that include Bookman L, Century Schoolbook, Chancery L, Dingbats, Gothic L, Nimbus Mono L, Nimbus Mono No9 L, Nimbus Sans L, Palladio L and Standard Symbols L. Besides, a miscellaneous set is also supplied for free which includes Cyrillic, Kana and fonts derived from the free Hershey fonts. 

PostScript Fonts 

PostScript fonts are outline font specifications developed for professional digital typesetting that include Type 0, Type 1, Type 2, Type 3, Type 4, Type 5, Types 9,10 and 11, Type 14, Type 32 and Type 42. Type 0 is a composite font format and is composed of high-level font that references multiple descendant fonts. Known as PostScript Type 1, PS 1, T1, Adobe Type 1 and PostScript, Type 1 is the font format for single-byte digital fonts. It supports font hinting and can be used with Adobe Type Manager Software and PostScript printers.

Designed to be used with CFF (Compact Font Format), Type 2 is a character string format and offers a compact representation of the character description procedures. Type 3 consists of glyph defined full PostScript language but does not support hinting. Known as PostScript Type 3, PS 3, T3 and Adobe Type 3 offers some additional features such as specific shading, coloring and filling of patterns. The type 4 format is used to make fonts for printer font cartridges.

Known as CROM (Compressed ROM font), Type 5 is similar to the Type 4 format. The difference is that it is used for fonts stored in the ROM of a PostScript printer. Referred to as CID font types 0, 1 and 2 respectively, Type 9, 10 and 11 are CID keyed fonts for storing Types 1, 3 and 42 respectively. Type 14 or Chameleon font format consists of one Master font and a set of font descriptors. The font descriptors specify ways to adjust the master font to give a desired set of character shapes for a specific typeface. The format represents a large number of fonts in a small amount of storage space.

Type 32 is used in PostScript interpreters with version number 2016 or greater to download bitmap formats. The type 42 format allows PostScript capable printers to print TrueType fonts. It is called as PostScript wrapper around a TrueType font.

PostScript Printing   

Unlike other typical printer control languages, PostScript is a complete programming language of its own. Many formats can be transformed in  a PostScript file that can be viewed on displays and printed in original documents. It is primarily used in laser printers but can be adapted to non-PostScript devices easily. For example, if your printer does not support PostScript printing, all you need to do is to purchase a cartridge that contains PostScript and install it in your printer.

Laser printers combine best features of both printers and plotters and offer high quality line art and also generate pages of text and raster graphics. Laser printers can also position text and high-quality graphics on the same page. PostScript fully exploits these amazing features by offering a single control language that can be used on any brand of printer.

Encapsulated PostScript (EPS)

Encapsulated PostScript is a PostScript document conforming DSC (a set of standards for PostScript). It is a standard format to import and export PostScript language files in all environments. EPS files are reasonably predictable PostScript documents that describe an image or drawing and are able to contain any combination of graphics, images and text. It is the best graphic format for printing high-resolution illustrations. EPS files include a preview picture of the content so that user can have a simple preview of final output in any application. The content preview is available in three formats including IBM (tiff), Mac (PICT) and a platform independent preview called EPSI. There are a number of programs that save or convert text and vector art to EPS format such as GIMP, Adobe Illustrator, Inkscape, Adobe Photoshop (Newer Versions), GhostScript and CoreIDRAW. Printers with PostScript also have an option to save documents as EPS.

About the Author: Andrew Yeung is the Marketing Director of ComboInk, a leading online provider of premium printer ink cartridges, including Canon cartridges and HP deskjet cartridges. By purchasing a large volume from factory, ComboInk is able to sell laser toner cartridges at steep discounts, saving small businesses thousands in operating costs each year.