How to get mask from boundary()

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Hugo Daniel 2019-2-20

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/445942-how-to-get-mask-from-boundary

评论： Hugo Daniel 2019-2-21

采纳的回答： KSSV

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?

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KSSV 2019-2-20

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/445942-how-to-get-mask-from-boundary#answer_361842

在 MATLAB Online 中打开

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')

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KSSV 2019-2-21

在 MATLAB Online 中打开

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')