From CryptoDox, The Online Encyclopedia on Cryptography and Information Security
BPCS-Steganography (Bit-Plane Complexity Segmentation Steganography) is a type of digital steganography. Typically, it uses an image file in true color format (BMP image) for a vessel. It can conceal (or "embed") very large amount of "confidential" data file in the vessel. It is reported that the ordinary embedding capacity amounts to 50% (or more) of the vessel image size. The principle of the embedding is to replace "noisy" areas on each bit-plane of the vessel image with the confidential data. This steganography exploits the characteristecs of human vision system which can't see any shape information in a very noisy area on an image bit-plane. In the embedding process the image color value is transformed from the pure binary code system into the canonical gray code system because the canonical gray code keeps better image quality than pure binary code when the vessel is embedded with other data. Noisy area on the bit-plane is segmented according to a complexity measure for the binary image.