ROTHWELLEDGE_BASE - Base function for ROTHWELLEDGE.

Contents

Syntax

  [edgemap, mag, or] = ROTHWELLEDGE_BASE(I, sigma, low, alpha, samp, reduce);
  [edgemap, mag, or] = ROTHWELLEDGE_BASE(gx, gy, low, alpha, samp, reduce);

Acknowledgment

This function uses the C function developped Heath et al. for the comparative study in [HSSB97]; the mex file in ROTHWELL_MEX calls directly the code made available by the authors in the page: ftp://figment.csee.usf.edu/pub/Edge_Comparison/source_code/rothwell.src

See also

Ressembles: ROTHWELLEDGE, EDGECORNER_BASE, CANNYEDGE_BASE, CONGRUENCYEDGE_BASE, COMPASSEDGE_BASE, ANISOEDGE_BASE, ELDERZUCKEREDGE_BASE, KOETHEDGE_BASE, SDGDEDGE_BASE, PETROUEDGE_BASE. Requires: ROTHWELLEDGE_MEX.

Function implementation

function [edgemap,varargout] = rothwelledge_base(I, V, low, alpha, samp, reduce)

if nargin<5,  samp = 1;
    if nargin<6,   reduce = false;
    end
end; % we allow variable number of inputs

dealing with multispectral images

[X,Y,C] = size(I);

if C>1
    if (islogical(reduce) && ~reduce) || ...
            (ischar(reduce) && strcmpi(reduce,'eor'))
        % process channel by channel
        edgemap = false(X*samp, Y*samp, C);
        for i=1:nargout-1,
            varargout{i} = zeros(X*samp, Y*samp, C);
        end
        if isscalar(V), V = repmat(V, [1 1 3]);  end
        for c=1:C
            [edgemap(:,:,c), mag, or] = ...
                rothwelledge_base(I(:,:,c), V(:,:,c), low, alpha, samp);
            if nargout>=2,  varargout{1}(:,:,c) = or;   end
            if nargout==3,  varargout{2}(:,:,c) = mag;  end
        end
        if strcmpi(reduce,'eor')
            for c=1:C
                edgemap(:,:,1) = edgemap(:,:,1) | edgemap(:,:,c);
            end
            edgemap = bwmorph(edgemap(:,:,1),'thin',Inf);
        end
        return;

    elseif islogical(reduce) || ...
            (ischar(reduce) && any(strcmpi(reduce,{'isum','igray','imax'})))
        % at that point, if reduce is logical, it is necessarly true

        if C==3 && strcmpi(reduce,'igray')
            I = rgb2gray(rescale(I,0,1));

        elseif islogical(reduce) || strcmpi(reduce,'isum')
            if C==3
                I = 0.29*I(:,:,1) + 0.59*I(:,:,2) + 0.11*I(:,:,3);
                I = rescale(I,0,1);
            else
                I = sum(rescale(I,0,1), 3);
            end

        elseif strcmpi(reduce,'imax')
            I = max(rescale(I,0,1), [], 3);
        end

    end

end

I = rescale(I,0,255); % requirement when calling rothwelledge_mex...

set some internal parameter fo padding the input image (see function

if samp>1
    S =[samp samp];
    % perform interpolation channel by channel
    I = upscalexy_base(I, S, 'linear');
end

smooth_image of rothwell_mex

if isscalar(V)
    sigma = samp * V;
    gy = [];
    gauss_tail = 0.015;
    kwidth = ceil(sigma*sqrt(2*log(1/gauss_tail))+1); %
    A = padarray(I, [kwidth kwidth], 'symmetric', 'both');

elseif isnumeric(V)
    sigma = [];
    gy = V;
    if samp>1,  gy = upscalexy_base(gy, S, 'linear');  end
    A = I;
    kwidth = 0;
end

call the mex file

[edgemap, or, mag] = rothwelledge_mex(A, gy, sigma, low, alpha);

crop

if isscalar(V)
    edgemap = edgemap(kwidth+1:kwidth+X*samp,kwidth+1:kwidth+Y*samp);
end

outputs

if nargout>=2
    varargout{1} = mag(kwidth+1:kwidth+X*samp,kwidth+1:kwidth+Y*samp);
end
if nargout==3
    varargout{2} = or(kwidth+1:kwidth+X*samp,kwidth+1:kwidth+Y*samp);
end

end % end of rothwelledge_base