A scan line or scanline is one line, or row, in a raster scan

Raster scan

A raster scan, or raster scanning, is the rectangular pattern of image capture and reconstruction in television. By analogy, the term is used for raster graphics, the pattern of image storage and transmission used in most computer bitmap image systems...

ning pattern, such as a line of video

Video

Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...

 on a cathode ray tube

Cathode ray tube

The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...

 (CRT) display of a television set

Television set

A television set is a device that combines a tuner, display, and speakers for the purpose of viewing television. Television sets became a popular consumer product after the Second World War, using vacuum tubes and cathode ray tube displays...

 or computer monitor.

On older CRT screens the horizontal scan lines were visually discernible, even when viewed from a distance, as alternating colored lines and black lines. This is sometimes used today as a visual effect

Visual effects

Visual effects are the various processes by which imagery is created and/or manipulated outside the context of a live action shoot. Visual effects involve the integration of live-action footage and generated imagery to create environments which look realistic, but would be dangerous, costly, or...

 in computer graphics

Computer graphics

Computer graphics are graphics created using computers and, more generally, the representation and manipulation of image data by a computer with help from specialized software and hardware....

.

The term is used, by analogy, for a single row of pixel

Pixel

In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....

s in a raster graphics

Raster graphics

In computer graphics, a raster graphics image, or bitmap, is a data structure representing a generally rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other display medium...

 image.
Scan lines are important in representations of image data, because many image file formats 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 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

• Fax
  Fax
  Fax , sometimes called telecopying, is the telephonic transmission of scanned printed material , normally to a telephone number connected to a printer or other output device...
  
  
• Interlaced video
• Native resolution
  Native resolution
  The native resolution of a LCD, LCoS or other flat panel display refers to its single fixed resolution. As an LCD display consists of a fixed raster, it cannot change resolution to match the signal being displayed as a CRT monitor can, meaning that optimal display quality can be reached only when...
  
  
• Pixel
  Pixel
  In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
  
  
• Progressive video
• Raster scan
  Raster scan
  A raster scan, or raster scanning, is the rectangular pattern of image capture and reconstruction in television. By analogy, the term is used for raster graphics, the pattern of image storage and transmission used in most computer bitmap image systems...
  
  
• Scanline fill
• Scanline rendering
  Scanline rendering
  Scanline rendering is an algorithm for visible surface determination, in 3D computer graphics,that works on a row-by-row basis rather than a polygon-by-polygon or pixel-by-pixel basis...