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A raster image (or image in point mode) is a data structure that represents a rectangular array of pixels, or points of color, said raster, that can be viewed/displayed on a computer screen, on paper, or other display device.
The term raster (raster) comes from the latin rastrum ('rake'), which, in turn, derives from radere ("scratch"). The raster images are characterized according to their height and width in pixels (which determines the image resolution), or well depending on their intensity/depth of color (bits per pixel), which shows the amount of colors that can be stored in each pixel.
Unlike the vector graphics (image raster versus vector image), which represent an image with geometrical objects, the rasterized graphics are limited to storage of color in each pixel. The raster images are typically used to make digital photographs, capture of video and convert analog archives in digital archives, for example, by means of a scanner.
The amount of bits of color per pixel is the key to the quality of the image. A raster image that stores 24 bits of color per pixel information may represent more matrices of color as an image that stores 16 bits per pixel, but will have a level of less detail than a bitmap with 48 bits per pixel.
However, an image with a resolution of 640 x 480 pixels will seem smaller than an image of 1280 x 1024, although they may have the same quality.