**Name**

**align** Detect (maximal) meaningful segments

**Command Synopsis**

**align** [-a] [-d *d*] [-n *nl*] [-g *g*] [-e *eps*] [-c *crv*] *u* *out*

-a : to get all meaningful segments (maximal or not)

-dd: number of allowed gradient directions, default 16

-nnl: number of line directions to scan, default 96)

-gg: minimum gradient norm to define a direction, default 2.

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

-ccrv: store segments as curves (output, Flists)

u: input Fimage

out: result: 5-Flist (x1 y1 x2 y2 -log10(nfa))

**Function Summary**

Flist align (u , d , nl , eps , g , all , crv )

Fimage u ;

int *d , *nl ;

double *eps ;

float *g ;

char *all ;

Flists crv ;

**Description**

This module extracts ``meaningful alignments'' from an image.
An alignment is detected when a discrete segment of the image
contains a relatively high number of points for which the
direction orthogonal to the gradient (that is, the direction
of the level line passing through the point) is equal to the direction
of the segment modulo a given precision *p*. The detection is made
using a thresholding function balancing between the density of
aligned points and the length of the segment. This function ensures
that at most 10^{-eps} false detections could occur by chance
with random gradient directions (see [DMM00]).

The result is a 5-Flist, that has 0 element if no alignment was detected.
The `-c`

option store the detected segments as a collection of curves
(Flists), allowing direct visualization with the `fkview`

module.

**Version 1.1**

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

**Author**

Lionel Moisan