Advances in Visual Data Compression and Communication

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Chapter 8

Directional DCT Transform

8.1 Introduction

Most of the image compression schemes are constructed upon the identical architec-

ture of the 2D transform followed by entropy coding, for example, JPEG uses the

2D discrete cosine transform (DCT) and variable length coding (VLC) [129], and

JPEG 2000 uses the 2D wavelet transform and Embedded Block Coding with Op-

timized Truncation (EBCOT) [103, 130]. Either 2D DCT or 2D wavelet transform

is implemented by separable 1D transform in horizontal and vertical directions. A

serious drawback of these transforms is that they are ill-suited to approximate im-

age features with arbitrary orientation that is neither vertical nor horizontal. In these

cases, they result in large-magnitude high-frequenc ...