Editing Raster image processor

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[[File:RIP Data Flow.svg|thumb|300px|Generating the raster image data]]

A '''raster image processor''' ('''RIP''') is a component used in a [[printing]] system which produces a [[raster graphics|raster]] image also known as a [[bitmap]].<ref>{{Cite web |title=Raster Image Processor - PrintWiki |url=http://printwiki.org/Raster_Image_Processor |access-date=2023-01-02 |website=printwiki.org}}</ref><ref>{{cite web |title=Patent US6469805 - Post raster-image processing controls for digital color image printing |url=http://www.google.nl/patents/US6469805 |access-date=30 November 2014 |publisher=Google.nl}}</ref> Such a bitmap is used by a later stage of the printing system to produce the printed output. The input may be a page description in a high-level [[page description language]] such as [[PostScript]], [[PDF]], or [[Open XML Paper Specification|XPS]]. The input can also be or include bitmaps of higher or lower resolution than the output device, which the RIP resizes using an [[image scaling]] algorithm.

Originally a RIP was a [[19-inch rack|rack]] of electronic hardware which received the page description via some interface (e.g. [[RS-232]]) and generated a "hardware bitmap output" which was used to enable or disable each [[pixel]] on a real-time output device such as a [[Laser printing|laser printer]], an optical [[film recorder]], [[computer to film]], or [[computer to plate]].

A RIP can be implemented as a software module on a general-purpose computer, or as a firmware program executed on a [[microprocessor]] inside a printer. For high-end typesetting, standalone hardware RIPs are sometimes used. [[Ghostscript]], GhostPCL, and ColorBurst's Overdrive (for [[macOS]]) are examples of software RIPs. Every PostScript printer contains a RIP in its [[firmware]]. The RIP [[microprocessor|chip]] in a [[laser printing|laser printer]] sends its [[raster image]] output to the [[laser]].

Earlier RIPs retained backward compatibility with [[phototypesetting|phototypesetters]]/photosetters, so they supported the older languages. So, for example, Linotype RIPs supported CORA (RIP30).

==Stages of RIP==
# '''Interpretation''': This is the stage where the supported PDLs (page description languages) are translated into a private internal representation of each page. Most RIPs process pages serially, one page at a time, so the current machine state is only for the current page. After a page has been output, the page state is discarded to prepare for the next page.
# '''Rendering''': A process through which the private internal representation is turned into a [[continuous tone|continuous-tone]] bitmap. In practical RIPs, interpretation and rendering are frequently done together. Simple languages were designed to work on minimal hardware, so tend to "directly drive" the renderer.
# '''Screening''': In order to print, the continuous-tone image is converted into a [[halftone]] (pattern of dots). Two screening methods or types are ''amplitude modulation'' (AM) screening and ''stochastic'' or ''frequency modulation'' (FM) screening. In AM screening, dot size varies depending on object density—tonal values; dots are placed in a fixed grid. In FM screening, dot size remains constant and dots are placed in random order to create darker or lighter areas of the image; dot placement is precisely controlled by sophisticated mathematical algorithms.

==See also==
*[[Image tracing]] (raster-to-vector "conversion")
*[[Laser printing]]
*[[Raster graphics]]
*[[Vector graphics]]

==References==
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[[Category:Printing technology]]
[[Category:Printing terminology]]