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Chapter 9
Directional Filtering Transform
9.1 Introduction
In natural images, there usually exist many textures, lines, and edges. Along the
edges, sample intensities change smoothly; but across the edges they will change
dramatically even with a small shift from the edges. This kind of correlation shows
a strong anisotropic feature because it depends upon not only the distance of sam-
ples but also their link orientation. Furthermore, the link orientation often goes in
all directions rather than only the vertical or the horizontal. Traditional transforms
such as the discrete cosine transform (DCT) and discrete wavelet transform (DWT)
cannot handle this directional correlation well and energy compaction is not fully
achieved. Therefore, many ...