The anisotropic wavelet packet transform is an extension of the conventional wavelet (packet) transform where the basis can have different scales in different dimensions. As there are certain kinds of images with different behaviour in horizontal and vertical direction, anisotropic wavelet packet bases can be adapted more precisely to these images. Zero-tree image compression has already proved its efficiency on conventional wavelet transformed data as well as for wavelet packets. In this work, zero-tree methods are extended to work with anisotropic wavelet packets and coding results are shown for several types of images.
Rade Kutil, Rade Kutil,
"Zerotree image compression using anisotropic wavelet packet transform", Proc. SPIE 5150, Visual Communications and Image Processing 2003, (23 June 2003); doi: 10.1117/12.503124; https://doi.org/10.1117/12.503124