BPP

bpp

Bits Per Pixel. When encoding encoding a colour image the number of bits per pixel indicates the number of possible colours (or grayscales).

Typically bpp is one of:

BPP	Number of Colours	Description
1 bit	2	normally black and white (monochrome)
4 bit	16	normally a fixed colour palette or grayscale.
8 bit	256	normally a fixed colour palette or grayscale.
16 bit	65,536	normally 5 bits for red, 5 bits for blue and 6 bits for green. Thus 0-31 for red, 0-31 for blue and 0-63 for green.
24 bit	16,777,216	8 bits for each of red, green and blue, allowing each component of red, green and blue to be specified in the range 0 to 255.

other values have been in use but are less common or obsolete.