Truecolor

Truecolor (also spelled Truecolour; called Millions on a Macintosh) graphics is a method of storing image information in a computer's memory such that each pixel is represented by three or more bytes.

Generally one byte is used for each channel with the fourth byte (if present) being used either as an alpha channel data or simply ignored. Byte order is usually either RGB or BGR. However systems do exist with more than 8 bits per channel and these are often also referred to as truecolor (for example a 48-bit truecolor scanner).

One byte per channel gives 256 (2⁸) intensites for each of the channels which gives 16,777,216 colors for each pixel (often approximated as 16 million despite the fact its closer to 17 million). The reason this is called truecolour is that this is around the number of colours the human eye is able to detect.

Whilst an alpha channel is meaningless in a display buffer, 32 bit truecolour has become popular on the computer desktop because it simplifies drawing of translucent images on the screen (and is often a requirement for hardware acceleration of such drawing) allowing desktop environments to more easilly provide effects such as translucent windows, fading menus, and shadows.

See also