[IPOL announce] new article: Extraction of the Level Lines of a Bilinear Image

[announcements about the IPOL journal]

A new article is available in IPOL: https://www.ipol.im/pub/art/2019/269/

Pascal Monasse,
Extraction of the Level Lines of a Bilinear Image,
Image Processing On Line, 9 (2019), pp. 205–219.
https://doi.org/10.5201/ipol.2019.269

Abstract
We detail precisely an algorithm for the extraction of the level lines 
of a bilinear image, which is a continuous function interpolating 
bilinearly a discrete image. If we discard the levels of the discrete 
image, where topological difficulties arise, a level line is a 
concatenation of branches of hyperbolas. The algorithm tracks these 
branches and provides a sampling of the level lines in the form of 
closed polygons. If the level line contains a saddle point, the 
hyperbola degenerates to orthogonal segments, where an arbitrary but 
consistent choice is adopted for the tracking at the bifurcation. In any 
case, the extracted polygons are disjoint and enclose a bounded region. 
This allows to order the level lines in an enclosure tree hierarchy, 
which may be used for a variety of filters. Recovering this tree is a 
simple post-processing of the extraction algorithm.