Image coding using lattice vector quantization of wavelet coefficients

An image coding scheme has been introduced by the authors (see IEEE ICASSP, p.2297, 1990). This scheme involves two steps. A biorthogonal wavelet transform is applied to the original image, and wavelet coefficients are then vector quantized using the LBG (Linde, Buzo and Gray, 1980) method. The purpose of this work is to propose a new scheme for vector quantization of wavelet coefficients. The proposed method is based on lattice vector quantization. The application of the D ₄, E₈ and Barnes-Wall Λ₁₆ lattices is investigated. These lattices are used to encode wavelet coefficients whose PDFs are close to Laplacian. A variable-length coding method is applied and the trade-off between distortion and optimal rate is investigated. Experimental results on the Lena image using the Λ₁₆ lattice leads to a peak signal-to-noise ratio (PSNR) of 31.14 dB at 0.08 bpp. This result outperforms, to the authors knowledge, all other methods. Edges which are most of interest for image analysis are particularly sharp without any smoothing artefacts