Shape Independent Coding Using NURBS and Bézier Approximation and Interpolation Curves

In this paper a scheme of utilizing shape independent basis functions for the hierarchical multiresolution image compression is shown. For a given image texture region segmentation method is used. Following polygonal approximation of created segments causes a degradation of their boundaries. Using NURBS and Bézier interpolation and approximation segments’ boundaries are created, thus achieving an image mask. As an input of the three-level hierarchical encoder this image mask and image are used. The image mask and image are subsampled by a factor of 2 on each level. The hierarchical encoder encodes them shape independently. Especially for a very low bit rate image coding gives better results for objective criteria (PSNR). For segment approximation the 2D shape independent orthogonal transform (DCT II) is used. Splines encoding and decoding is very efficient, because only their control points need to be stored. The segment is coded with a modified code similar to the JPEG code. Keywords—NURBS, Bézier, image compression, segmentation, shape independent transform.