How to get mask from boundary()

Hi,

I have points that represents curve levels. With thoses, I can find the boundary (k) matrix:

x = [1 2 3 4 3 2];

y = [4 5 5 4 3 3];

k = boundary(x,y);

I would like to make a mask from this boundary, but the function "boundary" does not provide the same output that "bwboundaries" does. Therefore, I cannot make a mask.

So, how can I make a mask with this data?

Answer 1

[KSSV]

x = [1 2 3 4 3 2]';
y = [4 5 5 4 3 3]';
k = boundary(x,y);

plot(x,y,'.r')
hold on
patch(x(k),y(k),'k')

[Hugo Daniel]

It is interesting, but I don't understand how I can filter data with the output of "patch" like I do with a mask.

[KSSV]

how you planned filtering using mask??

[Hugo Daniel]

I tought I could make a matrix of 1 and 0 from this mask and perform a & command.

[KSSV]

you can make with this also....use meshgrid and inpolygon.

[Hugo Daniel]

I don't understant how to use "p" in meshgrid.

x = [1 2 3 4 3 2]';
y = [4 5 5 4 3 3]';
k = boundary(x,y);
plot(x,y,'.r')
hold on
p = patch(x(k),y(k),'k')
...?

[KSSV]

x = [1 2 3 4 3 2]';
y = [4 5 5 4 3 3]';
k = boundary(x,y);


x0 = min(x) ; x1 = max(x) ;
y0 = min(y) ; y1 = max(y) ;

[X,Y] = meshgrid(linspace(x0,x1),linspace(y0,y1)) ;
idx = inpolygon(X(:),Y(:),x(k),y(k)) ;
% X(~idx) = NaN ; 
% Y(~idx) = NaN ;

plot(x,y,'.r')
hold on
patch(x(k),y(k),'k') ;
plot(X(idx),Y(idx),'.r')
plot(X(~idx),Y(~idx),'.b')

[Hugo Daniel]

Wow, I could not think of a better result! Thanks!