Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

On the Farey sequence and its augmentation for applications to image analysis

Pratihar S., Bhowmick P.

International Journal of Applied Mathematics and Computer Science

2017

Vol. 27, no. 3

637--658

We introduce a novel concept of the augmented Farey table (AFT). Its purpose is to store the ranks of fractions of a Farey sequence in an efficient manner so as to return the rank of any query fraction in constant time. As a result, computations on the digital plane can be crafted down to simple integer operations; for example, the tasks like determining the extent of collinearity of integer points or of parallelism of straight lines—often required to solve many image-analytic problems—can be made fast and efficient through an appropriate AFT-based tool. We derive certain interesting characterizations of an AFT for its efficient generation. We also show how, for a fraction not present in a Farey sequence, the rank of the nearest fraction in that sequence can efficiently be obtained by the regula falsi method from the AFT concerned. To assert its merit, we show its use in two applications—one in polygonal approximation of digital curves and the other in skew correction of engineering drawings in document images. Experimental results indicate the potential of the AFT in such image-analytic applications.

Real Polygonal Covers of Digital Discs - Some Theories and Experiments

Bhowmick P., Bhattacharya Bhargab.B.

Fundamenta Informaticae

2009

Vol. 91, nr 3-4

487-505

There are several algorithms for digitization of a real disc (circle) to derive a digital disc, and also for finding the real disc corresponding to a digital disc. However, the correspondence of a digital disc with a regular polygon in the real plane is not well studied. This paper presents some theories and related experiments on setting the correspondence from a digital disc to its polygonal cover in the real plane. For an ideal regular polygon covering a digital disc, all the grid points of the digital disc should lie on and inside the polygon, and vice versa. That an ideal regular polygon corresponding to a digital disc is possible for some of the digital discs, especially for the ones having smaller radii, is shown. Further, for a disc whose ideal regular polygon is not possible, an approximate polygon, tending to the ideal one, is possible, in which the error of approximation can be controlled by the number of vertices of the approximate polygon. These (ideal or approximate) polygonal covers of digital discs have several applications in many problems of point set pattern matching. We have reported the conditions under which an ideal regular polygon always exists corresponding to a digital disc, and the conditions under which the existence of an ideal regular polygon becomes uncertain. Experimental results have been given to demonstrate the possibilities of approximation and the trade-off in terms of error versus the number of vertices in the approximate polygon.