PostScript
Template: Infobox file format / Maintenance / type missing template: Infobox file format / Maintenance / default missing template: Infobox file format / Maintenance / missing site
Template: Infobox file format / Maintenance / MagischeZahlHex missing %!
PostScript is a page description language that is developed under this name since 1984 by the company Adobe. It is usually used as a vector graphics format for documents and printers, but also provides a Turing - complete, stack -oriented programming language dar. PostScript is a further development of Inter Press.
Dissemination
PostScript has evolved over the years to become a standard in the printing industry, but was largely the Portable Document Format (PDF) displaced, which was also developed by Adobe and has taken many features of PostScript.
Desktop publishing programs have usually via a PostScript export function. In practice, however (for example, from any word processing programs ) generated using a PostScript printer driver, PostScript code from any application that can be sent either directly to a postscript -capable output device or written to a file. Individual pages or graphics in PostScript format can also be imported from desktop publishing programs and some other applications in the form of Encapsulated PostScript files.
In Unix-like operating systems, it is common for application programs to send print jobs to PostScript to the printer server or the local printing system. This converts the PostScript data, usually with the help of Ghostscript, in device-specific code to.
Operation
Graphics and printing pages are created as files in PostScript format to be able to output lossless in any size and resolution of output devices. These graphic elements and fonts are described as scalable vector graphics. Raster graphics can also be embedded; they will be rescaled depending on the resolution of the output device.
PostScript is a Turing - complete programming language. It is stack -oriented and works on the principle of reverse polish notation; Model was the Forth programming language. PostScript -capable output devices (especially printers and printing machines) are equipped with a Raster Image Processor (RIP), so an interpreter to hardware or software -based feature, which evaluates the PostScript program piece by piece and converts it into a raster image (see also PostScript pressure height). Through this sequential instruction execution has no direct access to individual pages in PostScript files. A free software implementation of such an interpreter, the software Ghostscript.
A sample program
A sample program is:
%! / Courier findfont % Select font Scale 20 scalefont % to font size 20 make setfont % to the current character set 50 50 moveto % (50, 50) set as the current cursor position ( Hello world!) Show % and there the text output showpage % spend page The program writes "Hello world! " At the position 50,50. If the coordinate system has not been modified, it starts at the bottom left.
PostScript Level
The functionality of PostScript was extended twice. The extensions are backward compatible with one exception.
Level 2
PostScript Level 2 is a fully backward- compatible extension of the PostScript specification, which works faster and more reliable than Level 1 Added for example, was the support of embedded JPEG image data. Some additional features were introduced in view of the interactive use with Display PostScript, especially the so-called "Inside Ness Testing", can be tested with the example, whether a dot (" mouse " ) is within a path.
PostScript 3
This version was published in 1997. Adobe removed the name component " level " in favor of a simpler name. An important extension is a new color model called DeviceN, which is to guarantee accurate colors as possible on all output devices. The DeviceN model supports the mapping of Hexachrome or duplex colorations, which previously could only be implemented by an ausseparierte into individual color separations pages.
The operating system NeXTSTEP used as so-called PostScript Display PostScript also for the screen display.
The graphics system used in Mac OS X Quartz, which can be understood as the successor of Display PostScript, uses a graph model, which is based on PDF and implements a subset of PDF 1.2. Programs that use quartz for their graphics output, so can easily create PDF files. The transparency function of PDF is not directly supported by Quartz, Mac OS X treats transparent objects in other ways.
PDF features such as hypertext and forms is also implemented differently in programs that use quartz as in the PDF standard, so that can not be called complete compatibility with PDF.
Fonts (fonts)
PostScript uses its own font formats whose glyphs are described with PostScript and which differ in particular from the standard on Apple and Windows platforms TrueType format.
PostScript and PDF
This also developed by Adobe Portable Document Format ( PDF) is modeled on PostScript. The main differences to PostScript are that PDF are much stricter structured and not a complete programming language. For example, it ensures that you can access targeted to any page of a PDF document. In PostScript, this requires previously to interpret the code of all the foregoing pages.
Postscripts graphic model has been adopted in PDF and expanded. Any PostScript files can therefore be converted into PDF files without loss of graphical information. Conversely, this is only possible if the PDF document to dispense missing elements such as transparency in PostScript. In addition, PDF fillable forms can, pop-up comments, video and audio material, contain semantic tags and other elements that go beyond Postscripts of functions.
Revision history
- PostScript Level 1: 1984
- Display PostScript: 1988
- PostScript Level 2: 1991
- PostScript 3: 1998
Related languages and formats
- Encapsulated PostScript ( EPS)
- Portable Document Format (PDF)
- Variable Print Specification ( VPS)
- Extensible Stylesheet Language - Formatting Objects (XSL -FO )
- Printer Command Language (PCL )