next up previous contents index
Next: align_mdl Up: Reference Previous: view_demo   Contents   Index

align

$ \bigcirc$Name


align Detect (maximal) meaningful segments




$ \bigcirc$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)

-d d : number of allowed gradient directions, default 16

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

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

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

-c crv : store segments as curves (output, Flists)

u : input Fimage

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




$ \bigcirc$Function Summary


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

Fimage u ;

int *d , *nl ;

double *eps ;

float *g ;

char *all ;

Flists crv ;




$ \bigcirc$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.




$ \bigcirc$Version 1.1


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


$ \bigcirc$Author


Lionel Moisan






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