Image coding using directional VQ of wavelet coefficients

A new method is proposed for encoding an image without blocky effects using wavelet transform. To exploit the correlations among decomposed wavelet coefficients more effectively, slender rectangular blocks of wavelet coefficients are used in vector quantization (VQ) instead of square blocks which have been used in most of the other VQ methods. Each block is selectively vector-quantized depending on the energy of the coefficients in the block. Simulation results show that the PSNR performance of the proposed method is improved by about 0.4 ~ 0.8 dB when compared with the ordinary square block VQ. The subjective quality of the reconstructed image is also improved with the reduction of blocky effects