Volume 34 #3

Contents

1. Variability of the pattern VEP parameters in children without visual impairment and questions of preclinical diagnostics
2. Three tactics for gene therapy of two congenital retinal diseases. Review
3. Discrimination of rippled spectra with different ripple densities
4. Method of iterative tomography reconstruction of cropped sinograms
5. ANALYSIS OF A STOPPING METHOD FOR TEXT RECOGNITION IN VIDEO STREAM USING AN EXTENDED RESULT MODEL WITH PER-CHARACTER ALTERNATIVES
6. Recognition of projectively transformed planar figures. XIV. New methods for projectively-invariant description of ovals, using an H-polar curve and dual points
7. Radial distortion correction for camera submerged under water

On the basis of the algorithms proposed for processing oval curves of a general form with a fixed position P either inside or outside the field of the figure, it is shown how 2 (at least) pairs of projectively-stable points called dual pairs (DP) are calculated on the previously introduced H-polar curve. Each DP defines a quartet of projectively- invariant positions on the contour of the oval (O). The four points found on the O contour are used to obtain the etalon of O (the invariant projection of O onto a certain quadrangle), while DP compositions (numbering more than two) are suitable for organizing small-sized descriptors of O. The procedures for calculating stable O vertices for the following cases are described: search for a DP with the use of a harmonic contour (sort of the H-polar curve localized inside O); search for the external position of P (DP on the Plucker polar curve of the pole P); introducing an ht-polar curve (the “symbiont” of the H- and the T-polar curves that we introduced earlier), as well as the invariant description of O, which does not require specifying P (using an additional smooth-closed contour obtained via preprocessing of O using all the vertices of its approximation). Most of the considered cases include model demonstrations of computing wurf mappings (WM) of O on the basis of a set of independent wurf functions for different scenarios of the input picture, including a new approach that uses a harmonic contour O to obtain invariant WMs.

Key words: oval, test pole, Plücker pole and polar curve, dual points of an H-polar curve, harmonic contour, wurf function, projectively invariant mapping, cevian

DOI: 10.31857/S0235009220030063

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