ANISORFILT - Morphological anisotropic diffusion.

Description
Syntax
Inputs
Property [propertyname propertyvalues]
Output
Examples
Reference
See also
Function implementation

Description

Perform the morphological anisotropic diffusion (erosion or dilation) using the orientation information derived from the anisotropic continous scale model of [BBW07] and numerical scheme therein.

Syntax

   u = ANISORFILT(I);
   u = ANISORFILT(I, method, niter, delta, nu, ...
                         'Property', propertyvalue, ...);

Inputs

I : an input image with size (X,Y,C), where C>1 when I is multichannel.

method : (optional) string setting the morphological operation applied; it is either:

'dil' for anisotropic dilation (typically when one wants to continue/ prolong bright structures on a dark background, like edge map continuation),
'ero' for anisotropic erosion (when continuing dark structures on a dark background);

default: method='dil'.

niter : (optional) number of iterations; default: niter=10.

delta : (optional) $\delta$ of the numerical scheme; default: delta=0.5.

nu : (optional) nonegative integer $\nu$ which influences the propagation of the structures in the normal to the gradient direction; default: nu=4.

Property [propertyname propertyvalues]

'rho', 'sig', 'der', 'int', 'samp' : see GSTSMOOTH and ANISOR for the description of these variables; default: rho=3, sig=1, der='fast', int='fast' and samp=1.

Output

u : output of the anisotropic diffusion scheme.

Examples

a=zeros(50,50); a(25,10:20)=1;  a(25,30:40)=1; % input
method='dil'; delta=.5; niter=5; nu=5; %orientation diffusion parameters
rho=3; sigma=1; der='sob'; int='fast'; samp=1; %derivation parameters
u=anisorfilt(a, method, niter, delta, nu, 'rho', rho, 'sig', sigma, ...
             'der', der, 'int', int, 'samp', samp);
figure, imagesc(u), colormap gray;

[x,y,a] = createleakcircle(60,'grid',20,5,128);  imshow(a);
method='dil'; delta=.5; niter=20; nu=5; %orientation diffusion parameters
rho=3; sigma=1; der='fast'; int='fast'; samp=1; %derivation parameters
u=anisorfilt(a, method, niter, delta, nu, 'rho', rho, 'sig', sigma, ...
             'der', der, 'int', int, 'samp', samp);
figure, imshow(u);
u = bwmorph(u>0.8,'thin',Inf);
figure, imshow(u);

Reference

[BBW07] M. Breuß, B. Burgeth and J. Weickert: "Anisotropic continuous-scale morphology", Proc. IbPRIA, LNCS 4478, pp. 515-522, Springer, 2007. http://www.springerlink.com/content/1hm264w86111m148/

Function implementation

function u = anisorfilt(I,varargin)

parsing parameters

error(nargchk(1, 23, nargin, 'struct'));
error(nargoutchk(1, 1, nargout, 'struct'));

% mandatory parameter
if ~(isnumeric(I) || islogical(I))
    error('anisorfilt:inputerror','a matrix is required in input');
end

% optional parameters
p = createParser('ANISORFILT');
% principal optional parameters
p.addOptional('method', 'dil', @(x)ischar(x) && any(strcmpi(x,{'dil','ero'})));
p.addOptional('niter', 10, @(x)isscalar(x) && x>0);
p.addOptional('delta', 0.5, @(x)isscalar(x) && x>0);
p.addOptional('nu', 4, @(x)isscalar(x) && x>=0);
p.addParamValue('rho', 3, @(x)isscalar(x) && isfloat(x) && x>=0);
p.addParamValue('sig', 1, @(x)isscalar(x) && isfloat(x) && x>=0);
p.addParamValue('der', 'fast', @(x)islogical(x) || (ischar(x) && ...
    any(strcmpi(x,{'matlab','vista','fast','conv','diag', ...
    'tap5','sob','opt','ana'}))));
p.addParamValue('int', 'fast', @(x)islogical(x) || (ischar(x) && ...
    any(strcmpi(x,{'matlab','conv','fast','ani'}))));
p.addParamValue('samp', 2, @(x)isscalar(x) && round(x)==x && x>=1 && x<=5);

% parse and validate all input arguments
p.parse(varargin{:});
p = getvarParser(p);

checking/setting parameter

% the sign of delta defines if the morphological operation is a dilation ('+'
% sign) or an erosion ('-' sign)
if strcmpi(p.method,'ero'),  p.delta = -p.delta;    end

perform the anisotropic diffusion

u = anisorfilt_base(I, p.niter, p.delta, p.nu, p.rho, p.sig, ...
    p.der, p.int, p.samp);

if p.disp
    figure, imagesc(rescale(u,0,1)), colormap gray, axis image off;
    title('continuous-scale anisotropic diffusion')
end

end % end of anisorfilt