The orientation adaptive lapped biorthogonal transform for efficient image coding
T. Tanaka, Yukihiko Yamashita · 2002
A lapped biorthogonal transform adapted for local directionality of an image is proposed. The proposed transform consists of overlapping basis functions and non-overlapping basis functions, where the basis functions' centers of symmetry are aligned. Because of the alignment, we can treat the image boundaries without special processing. In order to construct non-overlapping basis functions, we also introduce a transform that provides the optimal approximation of an original signal in a given subspace. In image coding, an image block is selectively transformed by one of the orientation adaptive transforms. Experimental results show that the use of adaptation improves the quality of decoded images.