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NARVAL >> NL_V: Vision > NL_V_ContourCornersFilt

NL_V_ContourCornersFilt

Extract the corners of an obstacle contour (false detection removal).

Calling Sequence

[Xs,Ys,Ns] = NL_V_ContourCornersFilt(X,Y,D,N,Lc,Tc,Tg,Dt)

Arguments

X :

X-coordinates of corners.

Y :

Y-coordinates of corners.

D :

Direction vector.

N :

Length vector.

:

Correlation mode.

:

Correlation threshold.

:

Gradient threshold.

:

Minimum distance between two corners.

:

X-coordinate of corners.

:

Y-coordinate of corners.

:

Length vector.

Description

NL_V_ContourCornersFilt extracts the corners of the obstacle contour defined by the coordinates of the corner [X,Y] (see NL_V_ContourCorners) and removes false detections in respect with the two thresholds and . D gives the direction vector ([1 2 3 4 5 6 7 8]) of each corner found in each object. N provides the numbers of corners for each object. Lc represents the correlation mode, e.g. the kernel width: 1:+x+, 2:++x++ and 3:+++x+++. Dt is the minimum distance between two corners. After a false detection scheme, real corners coordinates are stored in . finally provides the number of corners for each obstacle.

Examples

dt=getdate();
seed=dt(10);
rand('seed',seed);//initialization of the random values generator
no=4;//quantity of obstacles (rectangle)
L=1000;//squared area side
hm=100;//minimal height
hM=250;//maximal height
wm=100;//minimal width
wM=250;//maximal width
Al=[0 %pi/2 %pi -%pi/2];//available angles for obstacles
[Xs,Ys,X,Y,H,W,A]=NL_V_RectanglesCorners(no,L,hm,hM,wm,wM);//generation of obstacles
[P]=NL_V_PotentialRectangles(X,Y,H,W,A,L);//generation of obstacle matrix
z=10;//zoom factor
o=2;// 1=mean, 2=max, 3=min, 4=median
Pz=NL_V_MRA(P,z,o);//scale modification
[Pzx,Pzy]=size(Pz);//image size
w1=1;//window index
w2=2;//window index
scf(w1);
clf(w1);
grayplot(1:Pzx,1:Pzy,Pz);//graph visualization
xset("colormap",graycolormap(128));
scf(w2);
clf(w2);
[PEz]=NL_V_Erosion(Pz);//contour performance
Cont=Pz-PEz;//contour 1
[Contx,Conty]=size(Cont);//image size
grayplot(1:Contx,1:Conty,Cont);//graph visualization
xset("colormap",graycolormap(128));
[x,y,direction,n]=NL_V_ContourCorners(Cont);//Corners detection
lc=2;//correlation mode
DT=3;//minimum distance between two corners
Tcorel=1;//threshold
Tgrad=1;//threshold
[xs,ys,ns]=NL_V_ContourCornersFilt(x,y,direction,n,lc,Tcorel,Tgrad,DT)//application of NL_V_ContourCornersFilt

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