**Name**

**ll_edges** Extract maximal meaningful edges (contrasted pieces of level lines) from a Fimage

**Command Synopsis**

**ll_edges** [-e *eps*] [-s *step*] [-p *p*] [-t *tree*] [-z] *in* *out*

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

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

-pp: sampling precision (bilinear), default 2

-ttree: use a precomputed FLST tree

-z : use zero order instead of bilinear interpolation

in: input Fimage

out: output edges (Flists)

**Function Summary**

Flists ll_edges (in , tree , eps , step , precision , z )

Fimage in ;

Shapes tree ;

float *eps , *step ;

int *precision ;

char *z ;

**Description**

This modules computes all the level lines of an image
(with the same options `-s`

, `-p`

, `-z`

and `-t`

as the `ll_extract`

module) and keeps the most contrasted parts of them.
The detection is made using a thresholding function balancing between
the minimum contrast (gradient norm) along each part and the
corresponding length of the curve. This 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_boundaries`

detection, this
module can detect non-closed level lines, since each subpart of each
level line is considered.

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

**See Also**

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

**Version 1.0**

Last Modification date : Thu Nov 29 20:23:56 2001

**Author**

Lionel Moisan