Harmonic Wavelet Transform and Image Approximation

  • Authors:
  • Zhihua Zhang;Naoki Saito

  • Affiliations:
  • College of Global Change and Earth System Science, Beijing Normal University, Beijing, China 100875 and Department of Mathematics, University of California, Davis, USA 95616;Department of Mathematics, University of California, Davis, USA 95616

  • Venue:
  • Journal of Mathematical Imaging and Vision
  • Year:
  • 2010

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Abstract

In 2006, Saito and Remy proposed a new transform called the Laplace Local Sine Transform (LLST) in image processing as follows. Let f be a twice continuously differentiable function on a domain 驴. First we approximate f by a harmonic function u such that the residual component v=f驴u vanishes on the boundary of 驴. Next, we do the odd extension for v, and then do the periodic extension, i.e. we obtain a periodic odd function v *. Finally, we expand v * into Fourier sine series. In this paper, we propose to expand v * into a periodic wavelet series with respect to biorthonormal periodic wavelet bases with the symmetric filter banks. We call this the Harmonic Wavelet Transform (HWT). HWT has an advantage over both the LLST and the conventional wavelet transforms. On the one hand, it removes the boundary mismatches as LLST does. On the other hand, the HWT coefficients reflect the local smoothness of f in the interior of 驴. So the HWT algorithm approximates data more efficiently than LLST, periodic wavelet transform, folded wavelet transform, and wavelets on interval. We demonstrate the superiority of HWT over the other transforms using several standard images.