bits per pixel

hardware, graphics (bpp) The number of bits of information

stored per pixel of an image or displayed by a graphicsadapter. The more bits there are, the more colours can be

represented, but the more memory is required to store or

display the image.

A colour can be described by the intensities of red, green and

blue (RGB) components. Allowing 8 bits (1 byte) per

component (24 bits per pixel) gives 256 levels for each

component and over 16 million different colours - more than

the human eye can distinguish. Microsoft Windows [and

others?] calls this truecolour. An image of 1024x768 with

24 bpp requires over 2 MB of memory.

"High colour" uses 16 bpp (or 15 bpp), 5 bits for blue, 5 bits

for red and 6 bits for green. This reduced colour precision

gives a slight loss of image quality at a 1/3 saving on

memory.

Standard VGA uses a palette of 16 colours (4 bpp), each

colour in the palette is 24 bit. Standard SVGA uses a

palette of 256 colours (8 bpp).

Some graphics hardware and software support 32-bit colour

depths, including an 8-bit "alpha channel" for transparency

effects.

(1999-08-01)