Foundations of Digital Image

01. Raster Image

In computer graphics, a raster graphics image, or bitmap, is a dot matrix data structure representing a generally rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other display medium. Raster images are 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. A 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). Each person in the above image can be thought as pixels. They just represent only one color by themselves but when they are together they constitute the image.

Celebrating 60 years of existence this year, North Korea holds out as the last Stalinist state in the world. Everyone is a pixel. Images are from the following website:





Another interesting analogy for the bitmap structure can be knitted items. Each knot, in different colors are single parts of a larger picture and when grouped together they can represent and perceived as a pattern or a figure. In this case a knot is directly analogous to a pixel which is the smallest building block of the image. Its size is considered as the smallest unit as 1×1, so the size is not a real parameter of this building block. It only consists of a color.

Knitting Stitch




William Betts

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