Hi guys, I am trying to create a magnetic field from an image contour and an attempt to create an active contour model. I have a function which takes the image derivative via a Guassian:(adsbygoogle = window.adsbygoogle || []).push({});

and now i need to take the curl of those image derivatives to get the pseudo magnetic field. having a bit of trouble with that though:Code (Text):function J=ImageDerivatives2D(I,sigma,type)

% Gaussian based image derivatives

%

% J=ImageDerivatives2D(I,sigma,type)

%

% inputs,

% I : The 2D image

% sigma : Gaussian Sigma

% type : 'x', 'y', 'xx', 'xy', 'yy'

%

% outputs,

% J : The image derivative

%

% Make derivatives kernels

[x,y]=ndgrid(floor(-3*sigma):ceil(3*sigma),floor(-3*sigma):ceil(3*sigma));

switch(type)

case 'x'

DGauss=-(x./(2*pi*sigma^4)).*exp(-(x.^2+y.^2)/(2*sigma^2));

case 'y'

DGauss=-(y./(2*pi*sigma^4)).*exp(-(x.^2+y.^2)/(2*sigma^2));

case 'xx'

DGauss = 1/(2*pi*sigma^4) * (x.^2/sigma^2 - 1) .* exp(-(x.^2 + y.^2)/(2*sigma^2));

case {'xy','yx'}

DGauss = 1/(2*pi*sigma^6) * (x .* y) .* exp(-(x.^2 + y.^2)/(2*sigma^2));

case 'yy'

DGauss = 1/(2*pi*sigma^4) * (y.^2/sigma^2 - 1) .* exp(-(x.^2 + y.^2)/(2*sigma^2));

end

J = conv2(I,DGauss,'same');

anyone have any tips as the second script does not work. i can to the divergence and laplacian easily as they are just first and second derivatives, but the curl is proving a bit of a problem. Any help would be great thanks!Code (Text):% Squared magnitude of force field

Fx= Fext(:,:,1);

Fy= Fext(:,:,2);

% Calculate magnitude

sMag = Fx.^2+ Fy.^2;

% Set new vector-field to initial field

u=Fx; v=Fy;

for i=1:Iterations,

% First order image derivatives

Uxx=ImageDerivatives2D(u,Sigma,'x');

Uyy=ImageDerivatives2D(u,Sigma,'y');

Vxx=ImageDerivatives2D(v,Sigma,'x');

Vyy=ImageDerivatives2D(v,Sigma,'y');

% Compute curl and update vector field

u = u + cross(Uxx,Uyy,3);

v = v + cross(Vxx,Vyy,3);

end

Fext(:,:,1) = u;

Fext(:,:,2) = v;

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# Curl of Gaussian image derivatives matlab

Can you offer guidance or do you also need help?

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