Bit maps are arranged in one or more color planes. A color plane is an array of bit-map bits that contains color information.
The bit maps in each of the previous illustrations use the single bit-map plane format, which is the standard format for bit maps in OS/2 applications. In this format, a specified number of adjacent bit-map bits contains indexes to either a special color table of RGB values or actual RGB2 structures. Whether the application maps bits into an RGB or RGB2 structure depends on the bit-map format. All of the color information resides in a single plane.
The second color format uses more than one color plane. A common multiplane bit-map format is the three-plane format, in which one plane corresponds to the red pels, another to the green pels, and a third to the blue pels. Multiplane bit-map formats are rare in PM applications. Most bit maps are stored externally in a single-plane format, although the device driver (such as VGA) may internally convert them to the multiplane format.
The single-plane format can be converted internally to any multiplane format used by a device. You also can use a nonstandard number of bits to describe each pel, if supported by your output device. If you write your own presentation driver, it must be able to convert the standard bit-map formats to its own internal format.
An application can determine which color-plane format a device supports by calling GpiQueryDeviceBitmapFormats.