Editing Scan line

{{Short description|One row in a raster scanning pattern}}

[[File:Mitsubishi CS-40307 CRT Television Close-up.jpg|thumb|Scanlines on a Mitsubishi CS-40307 CRT color television. The fine dots through the bright scanlines are due to the [[shadow mask]].]]
[[File:Videosignal scanline.jpg|thumb|right|[[PAL]] video signal scan line. From the left: horizontal [[sync pulse]], [[Analog television#Structure of a video signal|back porch]] with [[color burst]], signal itself, [[Analog television#Structure of a video signal|front porch]], sync pulse, back porch with color burst, video portion of the next scan line. The signals from multiple lines are overlaid, showing shaded areas instead of a single curve.]]

A '''scan line''' (also '''scanline''') is one line, or row, in a [[raster scan]]ning pattern, such as a line of [[video]] on a [[cathode-ray tube]] (CRT) display of a [[television set]] or [[computer monitor]].<ref>
{{cite book
 | title = Dictionary of Video and Television Technology
 | author = Keith Jack and Vladimir Tsatsulin
 | publisher = Newnes
 | year = 2002
 | isbn = 978-1-878707-99-4
 | page = 242
 | url = https://books.google.com/books?id=4Hsh7J0d1DwC&q=scan-line+video+display+computer+television&pg=PA242
 }}</ref>

On CRT screens the horizontal scan lines are visually discernible, even when viewed from a distance, as alternating colored lines and black lines, especially when a [[progressive scan]] signal with below maximum vertical resolution is displayed.<ref>{{cite news |author=Wesley Fenlon |date=15 January 2014 |title=In Search of Scanlines: The Best CRT Monitor for Retro Gaming |publisher=Tested |url=http://www.tested.com/tech/gaming/456719-best-crt-retro-games/ }}</ref> This is sometimes used today as a [[visual effects|visual effect]] in [[computer graphics]].<ref>{{cite news |author=Gabriel B. |date=December 2012 |title=Freeware Friday: Maldita Castilla |publisher=Blistered Thumbs |url=http://www.blisteredthumbs.net/2012/12/ff-maldita-castilla/ |archive-url=https://web.archive.org/web/20140227074522/http://www.blisteredthumbs.net/2012/12/ff-maldita-castilla/ |archive-date=2014-02-27 }}</ref>

The term is used, by analogy, for a single row of [[pixel]]s in a [[raster graphics]] image.<ref>
{{cite book
 | title = Practical algorithms for 3D computer graphics
 | author = Robin Stuart Ferguson
 | publisher = A K Peters, Ltd
 | year = 2001
 | isbn = 978-1-56881-154-3
 | page = 104
 | url = https://books.google.com/books?id=bBOxUmw83jUC&q=scanline+row-of-pixels&pg=PA104
 }}</ref>
Scan lines are important in representations of image data, because many [[image file format]]s have special rules for data at the end of a scan line. For example, there may be a rule that each scan line starts on a particular boundary (such as a byte or word; see for example [[BMP file format]]). This means that even otherwise compatible raster data may need to be analyzed at the level of scan lines in order to convert between formats.

==See also==
*[[Flicker (screen)]]
*[[Interlaced video]]
*[[Scanline rendering]]
*[[Stroboscopic effect]]

== References ==
{{reflist}}

{{Display technology}}

[[Category:Computer graphics]]
[[Category:Image processing]]
[[Category:Display technology]]
[[Category:Video signal]]
[[Category:Television technology]]
[[Category:Television terminology]]


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