HESSMOOTH_BASE - Base function for HESSMOOTH.

Contents

Syntax

   [H, gx, gy] = HESSMOOTH_BASE(I, rho, sig, der, int, samp, hsize, gn, tn, thez, sigt);

See also

Ressembles: HESSMOOTH, GSTSMOOTH_BASE. Requires: GRDSMOOTH_BASE, GRD2HESS_BASE, UPSCALEXY_BASE.

Function implementation

function [H,gx,gy,gxx,gyy,gxy] = ...
    hessmooth_base(I,rho, sig, der, int, samp, hsize, gn, tn, thez, sigt)

setting internal variables

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

define the filter window size: it is passed in order to constrain the smoothing and integration window size

if ~iscell(hsize)
    if length(hsize)==2,   j=2;
    else                   j=1;  end
    tmp = hsize;   hsize = cell(2,1);
    if ~isempty(tmp)
        hsize{1} = tmp(1);  hsize{2} = tmp(j);
    end
    % when hsize=[], then it is set a a cell of empty matrices
end

1st order derivation: compute the gradient (gy: vertical, gx: horizontal) for each channel

[gy,gx] = grdsmooth_base(I, sig, der, hsize{1}, 'ij');
gy = -gy;

interpolation following the recommandation of [Koth03]

if samp>1
    S =[samp samp]; % interpolation of a factor samp in X- and Y-directions
    % perform interpolation channel by channel
    gx = upscalexy_base(gx, S, 'linear');
    gy = upscalexy_base(gy, S, 'linear');
end

if gn
    d = sqrt( gx.^2 + gy.^2 );
    d(d<eps) = 1;
    gx = gx ./ d; gy = gy ./ d;
end

[gxx,gyy,gxy] = grd2hess_base(gx, gy, rho, der, int, ...
    hsize{2}, samp, tn, thez, sigt);

H(:,:,1,1) = gxx(1:samp:end,1:samp:end);
H(:,:,2,2) = gyy(1:samp:end,1:samp:end);
H(:,:,1,2) = gxy(1:samp:end,1:samp:end);
H(:,:,2,1) = H(:,:,1,2);

end % end of hessmooth_base