Embedded Wavelet Coding of Arbitrarily Shaped Objects

This paper presents an embedded zerotree wavelet coding technique for the compression of arbitrarily shaped 2-D objects. The wavelet decomposition is carried out with an optimized, biorthogonal, shape adaptive discrete wavelet transform (SA DWT) which performs non-expansive multiresolution decompositions of arbitrary image regions. The proposed SA DWT is defined for even-length, symmetric wavelet filters such as the 6-10 filters. The processing at region boundaries is carried out via reflection, followed by an optimization stage which requires only a few operations per boundary pixel. The computationally inexpensive optimization results in an additional performance gain of up to 0.5 dB compared to the plain reflection based scheme.