Bit-length expansion for digital images

Bit-length (i.e., resolution of signal amplitude) of digital images is decided by the quantization. The bit-length expansion technique is necessity for the high-quality display such as the liquid crystal display (LCD) and the plasma display. Since, these displays have more the 10 bit resolution for each color component. However, in general, color image signals are defined by 8 bit resolution for each component. Moreover, the bit-length expansion technique is also necessary for low bit-length images, which are observed the pseudo-contour. In this paper we propose the bit-length expansion method using adaptive window length filtering. We show that the excellent bit-length expanded images are obtained by the proposed method.