Find sphere fit on binary matrix

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Lieke Pullen
Lieke Pullen 2022-2-18
评论： Lieke Pullen 2022-2-21
Hi all,
I have a (239,239,85) binary matrix in which the 1's correspond to the mask of a geometrical shape (see attachment). I want to fit a sphere around it, so that it fits best to the binary mask. I have already tried this: https://nl.mathworks.com/matlabcentral/fileexchange/34129-sphere-fit-least-squared, but that does not work since the matrix is singular. Can anybody help me out? Thanks in advance!
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Walter Roberson
Walter Roberson 2022-2-18
If the matrix is singular then enter the data all lies in the same plane or else you are passing the wrong information to the fitting function.

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KSSV
KSSV 2022-2-18
load('matrixfit.mat')
[m,n,p] = size(tumor3) ;
[X,Y,Z] = ndgrid(1:m,1:n,1:p) ;
k = tumor3(:) ;
x = X(:) ;
y = Y(:) ;
z = Z(:) ;
P = [x(k==1) y(k==1) z(k==1)] ;
[Center,Radius] = sphereFit(P) ; % Use that file exchange function
I got:
Center = [100.8695 103.3629 37.2319] ;
Radius = 3.0785 ;
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Torsten
Torsten 2022-2-21
Usually,
solid_sphere= sqrt((X-Center(1)).^2 + (Y-Center(2)).^2 + (Z-Center(3)).^2) <= radius ;
Is it different in your case ?
Lieke Pullen
Lieke Pullen 2022-2-21
I think so, since I have made a linspace varying from -119 to -119 (for x and y), and from -43 to 43 for z. I used the equation you mentioned in the following script:
array_x=239; array_y=239; array_z=85;
sphere=create_sphere(round(Radius),array_x,array_y, array_z, round(Center));
function solid_sphere=create_sphere(radius,array_x,array_y, array_z,Center)
[X,Y,Z]=meshgrid(0:1:array_x-1, 0:1:array_y-1, 0:1:array_z-1);
solid_sphere= sqrt((X-madCenter(1)).^2 + (Y-Center(2)).^2 + (Z-Center(3)).^2) <= radius ;
end
But that also does not give me the right center unfortunately.

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