bits per pixel
(bpp) The number of bits of information stored per pixel of an image or displayed by a graphics adapter. 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.
Last updated: 1999-08-01