IMERAGRAD - Morphological gradient ERAGRAD.

Contents

Description

Compute the so-called ERAGRAD operation described in [BG09] consisting of a morphological gradient followed by an erosion.

Syntax

    E = IMERAGRAD(I);
    E = IMERAGRAD(I, shape);
    E = IMERAGRAD(I, shape, s1);
    E = IMERAGRAD(I, shape, s1, s2);

Inputs

I : input image of size (X,Y,C), with C>1 when I is multispectral.

shape, s1, s2 : optional arguments defining the SE used by the elementary operators called by IMERAGRAD; see function FLATSTREL for further explanation; default: shape='square', s1=3, s2=[].

Outputs

E : filtered image of same size as I output by the ERAGRAD operator.

Reference

[BG09] R. Bellens and S. Gautama: "Erosion after gradient (ErAGrad) morphological profile", Proc. IEEE International Geoscience & Remote Sensing Symposium, 2009. http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5418079

See also

Ressembles: IMCLOSE, IMRCLOSE, IMRECONSTRUCTBY. Requires: IMERAGRAD_BASE, FLATSTREL.

Function implementation

function E = imeragrad(I, varargin)

if isempty(ver('images'))
    error('imeragrad:errortoolbox', 'Image Processing toolbox required');
end

error(nargchk(1, 12, nargin, 'struct'));
error(nargoutchk(1, 1, nargout, 'struct'));

parsing parameters

if ~isnumeric(I)
    error('imeragrad:inputparameter','a matrix is required in input');
end

% optional parameters
p = createParser('IMERAGRAD');

p.addOptional('se', 'disk', @(x) strcmp(class(x),'strel') || ...
    (ischar(x) && any(strcmpi(x,{'disk','rectangle','square','diamond', ...
                'line','periodicline','arbitrary','octagon','pair'}))));
p.addOptional('s1', 3:2:10, @(x)isnumeric(x));
p.addOptional('s2', [], @(x)isnumeric(x));

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

checking/setting variables

if ischar(p.se)
    shape = p.se;
    N = length(p.s1);

    if ~iscell(p.s1),  p.s1 = num2cell(p.s1);  end
    if ~iscell(p.s2),
        if isempty(p.s2)
            p.s2 = cell(N,1);
        else
            if isscalar(p.s2),  p.s2 = repmat(p.s2, 1, N);  end;
            p.s2 = num2cell(p.s2);
        end
    end

    p.se = cell(N,1);
    for i=1:N
        p.se{i} = flatstrel(shape, p.s1{i}, p.s2{i});
    end

end

main processing

E = imeragrad_base(I,p.se);

display

if p.disp
    figure, imagesc(rescale(E)), axis image off, title('erosion after gradient');
    if size(E,3)==1,  colormap gray;  end
end

end % end of imeragrad