i
i
i
i
i
i
i
i
Part III
Directional Transforms
This part studies directional transforms, another important component in image
and video compression. Natural images inherently contain rich directional structures,
beyond simple horizontal or vertical lines, as in the contemporary digital images we
perceived today. It is true that conventional rectilinear transforms we have been us-
ing to represent images are unable to fully capture such directional correlations. For
any transform to become superior in coding of natural images, not only does it need
to properly capture the directional correlations, it also needs to generate the trans-
form coefficients in such a way that they can be optimally encoded by subsequent
entropy coding. It is based on such challenging ...