Investigating lossy image coding using the PLHaar transform

Summary form only given. We developed the piecewise-linear Haar (PLHaar) transform (Senecal, J.G. et al., Proc. 12th Pacific Conf. on Computer Graphics and Appl., p.371-80, 2004), an integer wavelet-like transform. PLHaar does not have dynamic range expansion, i.e., it is an n-bit to n-bit transform. To our knowledge, PLHaar is the only reversible n-bit to n-bit transform that is suitable for lossy and lossless coding. We are investigating PLHaar´s use in lossy image coding. Preliminary results from thresholding transform coefficients show that PLHaar does not produce objectionable artifacts like previous n-bit to n-bit transforms, such as that of Honyang Chao et al. (CFH) (see Advances in Computational Mathematics, Lect. Notes In Pure and App. Math., vol.202, p.13-38, 1999). Also, at lower bitrates PLHaar images have increased contrast. For a given set of CFH and PLHaar coefficients with equal entropy, the PLHaar reconstruction is more appealing, although the PSNR may be lower.