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ll_boundaries

$ \bigcirc$Name


ll_boundaries Extract meaningful boundaries (contrasted level lines) from a Fimage




$ \bigcirc$Command Synopsis


ll_boundaries [-e eps] [-a] [-w] [-s step] [-p p] [-t tree] [-z] in out



-e eps : -log10(max. number of false alarms), default 0

-a : get all contrasted level lines (not only maximal ones)

-w : select weak maximality

-s step : quantization step (bilinear), default 1.

-p p : sampling precision (bilinear), default 2

-t tree : use a precomputed FLST tree

-z : use zero order instead of bilinear interpolation

in : input Fimage

out : output boundaries (Flists)




$ \bigcirc$Function Summary


Flists ll_boundaries (in , tree , eps , all , step , precision , z , weak )

Fimage in ;

Shapes tree ;

float *eps , *step ;

int *precision ;

char *all , *z , *weak ;




$ \bigcirc$Description


This modules computes all the level lines (that is, the connected components of the boundaries of the level sets) of an image (with the same options -s, -p, -z and -t as the ll_extract module) and keeps the most contrasted ones. The detection is made using a thresholding function balancing between the minimum contrast (gradient norm) along the curve and the length of the curve. Unless -a option is specified, only on representant (the most meaningful one) is kept for each monotone sequence of meaningful level lines (that is, a sequence of level lines included in each others, with no inclusion branching and no contrast reversal). The thresholding function ensures that at most 10-eps false detections could occur by chance with independent random gradient values (see [DMM01]).


Notice that contrary to the ll_edges detection, this module is constrained to keep full (ie closed) level lines and cannot break them into parts.


The result is a collection of curves stored in a Flists structure.




$ \bigcirc$See Also


fderiv, fhisto, flst, flstb_boundary, flst_bilinear, flst_boundary, flstb_quantize, fsaddles, sintegral.




$ \bigcirc$Version 1.1


Last Modification date : Tue Apr 8 16:46:18 2003


$ \bigcirc$Author


Lionel Moisan






next up previous contents index
Next: ll_edges Up: Reference Previous: ll_boundaries2   Contents   Index
mw 2004-05-05