Editing CUPS (section)

==== Filtering process ====
The filtering process works by taking input data pre-formatted with six arguments:

# the job ID of the print job
# the user name
# the job name
# the number of copies to print
# any print options
# the filename (though this is unnecessary if it has been redirected from [[standard input]]).<ref name="filters_sdd"/>

It then determines the type of data that is being input and the filter to be used through the use of the MIME databases; for instance, image data will be detected and processed through a particular filter, and HTML data detected and processed through another filter.

CUPS can convert supplied data either into [[PostScript]] data or directly into raster data. If it is converted into PostScript data an additional filter is applied called a ''prefilter'', which runs the PostScript data through another PostScript converter so that it can add printer-specific options like selecting page ranges to print, setting ''n''-up mode and other device-specific things.<ref name="pstops">{{cite web|work=[[Easy Software Products]]|publisher=CUPS Software Administrators Manual|url=http://www.cups.org/doc-1.1/sdd.html#3_7_5|title=pstops|access-date=January 9, 2007|url-status=dead|archive-url=https://web.archive.org/web/20070110180805/http://www.cups.org/doc-1.1/sdd.html#3_7_5|archive-date=January 10, 2007}}</ref> After the pre-filtering is done, the data can either be sent directly to a CUPS [[#Backends|backend]] if using a PostScript printer, or it can be passed to another filter like [[Foomatic]] by [[linuxprinting.org]]. Alternatively, it can be passed to [[Ghostscript]], which converts the PostScript into an intermediary ''CUPS-raster'' format.<ref name="cups-raster MIME type">The MIME type for the CUPS raster format is application/vnd.cups-raster.</ref> The intermediary raster format is then passed onto a final filter which converts the raster data to a printer-specific format. The default filters included with CUPS include:

* raster to [[Printer Command Language|PCL]]
* raster to [[ESC/P]] or [[ESC/P2]] (an [[Epson]] printer language, now largely superseded by their new ESC/P-Raster format)
* raster to [[Dymo]] (another printer company).
* raster to Zebra Programming Language or ZPL (a [[Zebra Technologies]] printer language)

{{As of | 2009}} other proprietary languages like GDI or SPL (Samsung Printer Language) are supported by Splix, a raster to SPL translator.<ref>{{Cite web|url=http://splix.sourceforge.net/|title=SPL driver for UNIX|website=splix.sourceforge.net}}</ref>

However, several other alternatives can integrate with CUPS. [[HPLIP]] (previously known as HP-IJS) provides Linux+CUPS drivers for HP printers, [[Gutenprint]] (previously known as Gimp-Print) is a range of high-quality printer drivers for (mostly) inkjet printers, and [[TurboPrint]] for Linux has another range of quality printer drivers for a wide range of printers.