Abstract
In this article, an efficient image coding scheme that takes advantages of feature vector in wavelet domain is proposed. First, a multiโstage discrete wavelet transform is applied on the image. Then, the wavelet feature vectors are extracted from the waveletโdecomposed subimages by collecting the corresponding wavelet coefficients. And finally, the image is coded into bitโstream by applying vector quantization (VQ) on the extracted wavelet feature vectors. In the encoder, the wavelet feature vectors are encoded with a codebook where the dimension of codeword is less than that of wavelet feature vector. By this way, the coding system can greatly improve its efficiency. However, to fully reconstruct the image, the received indexes in the decoder are decoded with a codebook where the dimension of codeword is the same as that of wavelet feature vector. Therefore, the quality of reconstructed images can be preserved well. The proposed scheme achieves good compression efficiency by the following three methods. (1) Using the correlation among wavelet coefficients. (2) Placing different emphasis on wavelet coefficients at different decomposing levels. (3) Preserving the most important information of the image by coding the lowestโpass subimage individually. In our experiments, simulation results show that the proposed scheme outperforms the recent VQโbased image coding schemes and waveletโbased image coding techniques, respectively. Moreover, the proposed scheme is also suitable for very low bit rate image coding. ยฉ 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 15, 123โ130, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.20045