Glossary definition of Pixel

Pixel is the smallest picture element found on a display. In the colour screens of televisions, computers and mobile devices, there will be an array of evenly spaced pixels covering the whole of the screen area. For example, in a mobile phone with an LCD display measuring 128 pixels wide by 160 pixels high, there will be 128 x 160 or 20,480 pixels in total. Generally, the greater the number of pixels, the sharper and more detailed will be the image that can be displayed. On the contrary, if the display has a low number of pixels (a small dpi), then this will be noticeable in the images displayed, and diagonal lines will appear to be jagged.

In a black and white display each pixel will only be required to be on or off, meaning that only one bit of digital data is required define these two states for each pixel. However, in a greyscale display more than one bit will be required to set the various shades of grey for each pixel. For example, two bits per pixel will enable black, white, and two shades of grey to be displayed.

In a colour display, there will be three sub-pixels (one each for red, green and blue), which are then blended to define the colour of each pixel, and many more bits of data are necessary to define all the various graduations of colour. The number of distinct colours that a display can represent depends on the number of bits per pixel that are used. The standard numbers of bits per pixel used in real colour displays are:

12 bits per pixel = 4,096 colours 16 bits per pixel = 65,536 colours 24 bits per pixel = 16,777,216 colours

Mobile phone displays are now produced using 16 bits or 12 bits per pixel, whereas computer monitors can support the full 24-bit colour (known as truecolour).

Phones tagged with Pixel