Raster scan, or raster scanning: is the pattern of image
detection and reconstruction in television, and is the pattern of
image storage and transmission used in most computer image systems.
The word raster comes from the Latin word for a rake, as the
pattern left by a rake resembles the parallel lines of a scanning
raster.
Picture element:
In a raster scan, an image is cut up into successive samples
called pixels, or picture elements, along scan lines. Each scan
line can be transmitted as it is read from the detector, as in
television systems, or can be stored as a row of pixel values in an
array in a computer system. On a television receiver or computer
monitor, the scan line is turned back to a line across an image, in
the same order. After each scan line, the position of the scan line
is advanced, typically downward across the image in a process known
as vertical scanning, and a next scan line is detected,
transmitted, stored, retrieved, or displayed. This ordering of
pixels by rows is known as raster order, or raster scan order.
