Chan vese Curvature

I found this function to take the curvature but i am not sure what exactly does .Can anyone help me? The code is:

function curvature=get_curvature(phi)
dx=( shiftR(phi)-shiftL(phi))/2;
dy=( shiftU(phi)-shiftD(phi))/2 ;
dxplus=shiftR(phi)-phi ;
dyplus=shiftU(phi)-phi ;
dxminus=phi-shiftL(phi);
dyminus=phi-shiftD(phi);
dxplusy =(shiftU(shiftR(phi))-shiftU(shiftL(phi)))/2;
dyplusx =(shiftR(shiftU(phi))-shiftR(shiftD(phi)))/2 ;
dxminusy=(shiftD(shiftR(phi))-shiftD(shiftL(phi)))/2 ;
dyminusx=(shiftL(shiftU(phi))-shiftL(shiftD(phi)))/2 ;
nplusx = dxplus./sqrt(eps+(dxplus.^2 )+((dyplusx+dy)/2).^2 );
nplusy = dyplus./sqrt(eps+(dyplus.^2 )+((dxplusy+dx)/2).^2 ) ;
nminusx= dxminus./sqrt(eps+(dxminus.^2)+((dyminusx+dy)/2).^2);
nminusy= dyminus./sqrt(eps+(dyminus.^2)+((dxminusy+dx)/2 ).^2);
curvature=((nplusx-nminusx)+( nplusy-nminusy )/ 2 ) ;

    function shift =shiftD(M)
    shift=shiftR(M')';

function shift =shiftL(M)
shift=[M(:,2:size(M,2)) M(:,size(M,2))];

function shift=shiftR(M)
shift=[M(:,1) M(:,1:size(M,2)-1)];

function shift=shiftU(M)
shift=shiftL(M');

Is real the curvature?