RASTER GRAPHICS

In computer graphics, a raster graphics image, digital image, or bitmap, is a data structure representing a generally rectangular grid of pixels, or points of color, viewable via a computer monitor, paper, or other display medium. Raster images are commonly stored in image files with varying formats.
A bitmap corresponds bit-for-bit with an image displayed on a screen, generally in the same format used for storage in the display's video memory, or maybe as a device-independent bitmap. Bitmap is technically characterized by the width and height of the image in pixels and by the number of bits per pixel (a color depth, which determines the number of colors it can represent).
The printing and prepress industries know raster graphics as contones (from "continuous tones") and refer to vector graphics as "line work".
The word "raster" has its origins in Latin rastrum (a rake) and Latin radere (to scrape), and recalls metaphorically the systematic sampling of a grid-pattern of individual pixel-spaces with a view to representing an overall image.