i
i
i
i
i
i
i
i
Chapter 7
Directional Wavelet Transform
7.1 Introduction
The past decade has seen increased sophistication and maturity of wavelet-based
image compression technologies. Within the family of mathematical transforms for
image coding, discrete wavelet transform has unseated discrete cosine transform
(DCT) [127–129] as the transform of choice. The wavelet-based JPEG 2000 inter-
national standard for still image compression [130] not only obtains superior com-
pression performance over the DCT-based old JPEG standard [129], but also offers
scalability advantages in reconstruction quality and spatial resolution that are desir-
able features for many consumer and network applications.
However, the prevailing practice of 2D wavelet transform has a