bitmap	An image composed of binary pixels (black & white)

grayscale
	An image composed of gray levels (using 2 to 8 bits, usually
	8 bits).  May be mapped or unmapped.

RGB, 24bit
	An image which contains 3 8bit values of red, green, and
	blue for each pixel.  They are by definition unmapped.

mapped image, mapped color image
	A mapped image contains a single plane of values, 1 to 8 bits
	(usually 8, although 4-7 are also found), and a colormap
	which has three vectors of color values for red, green and
	blue.

unmapped image
	Either 8 bit grayscale or 24bit (RGB) color.
	The unmap

	