index > 2.1.4 Representation of data in computer systems


Every image that is displayed on an electronic device is composed of tiny squares known as pixels. These are the smallest elements of an image. The number of bits used for a pixel can determine the amount of colours that can be produced by each square; 1 bit can represent either black or white (either a 0 or 1), 2 bits can represent 4 colours, 8 bits (a byte) can represent 256 colours and 16 bits (2 bytes) can represent up to 65,536 different colours. The more of these bits a pixel is made up of, the greater the colour-depth, measure in bits per pixel (bpp). Common colours depths are 16 bpp- high colour and 24 bpp- true colour.

A method of working out the possible amount of colours a pixel can produce is found in the formula 2xwhere x is the number of bits.

The computer is able to work out how to turn these binary values into the actual image because the file contains the information and instructions on how to do so, this is known as metadata.

The resolution of an image is the number of pixels per unit or the concentration of pixels. It is calculated in pixels per inch (ppi). The more pixels per inch, the more data can be stored and the more colours that can be displayed. However an increased ppi, comes with the disadvantage of a large file size but a higher resolution. If a bitmapped image is displayed on a larger screen the actual image size does but the pixels get bigger so the image becomes more pixelated.