Costs and advantages of object-based image coding with shape-adaptive wavelet transform
Journal on Image and Video Processing
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A wavelet coding method for image data on arbitrarily shaped support applicable to the object-oriented coding of moving pictures, and to the efficient representation of texture data in computer graphics is proposed. Wavelet transform of arbitrarily shaped image is obtained by applying symmetrical extension technique at region boundaries and keeping the location of wavelet coefficient. For the entropy coding of the wavelet coefficients, zerotree coding technique is modified to work with arbitrarily shaped regions by treating missing (outside of the decomposed support) coefficients as insignificant and transmitting only those zerotree symbols which are in the decomposed support. The coding performance of the proposed method for several test images that include a person, a teapot and a necklace is compared to shape-adaptive DCT and ordinary DCT method applying low pass extrapolation to the DCT block containing the region boundaries. Experiments show that the proposed method has a better coding efficiency compared to SA-DCT and ordinary DCT method.