This research concerns compression of digital images consisting of
smoothly colored regions separated from each other by smooth contours.
Wavelet transforms combined with a nonlinear thresholding step are optimal when
catching point singularities, however, when trying to capture smooth
line singularities in a parsimonious manner they perform suboptimal.
We propose a geometrical method to deal with these inherent defficiencies of
wavelets. The proposed method using normal offsets transforms the input image
nonlinearly using only a series of scalar values.
Special attention is given on how to adapt the concept of normal
offsets towards the digital setting. Moreover, a local adaptive triangulation is
issued such that the method is able to sparsely represent higher dimensional singularities,
i.e., line singularities. The adaptive triangulation encourages the triangle
edges to settle themselves parallel with respect to the contour. At the
same time the locality of the triangulation method induces
hierarchical mesh structures which are well suited for compression
methods.
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