BWTHINUPSAMPLE - Upsampled morphological thinning of a binary image.

Contents

Description

Perform the morphological thinning of an upsampled binary image. Enable to deal with the indetermination of the thinning algorithm for binary structures of even width (in number of pixels).

Syntax

   BT = BWTHINUPSAMPLE(M);

Input

M : binary (logical) map with size (X,Y).

Output

BT : thinned map with size (2*X-1,2*Y-1).

See also

Ressembles: BWISOLATED, BWMORPH,

Function implementation

function BT = bwthinupsample(M)

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

[X,Y] = size(M);

M2 = zeros(2*X-1,2*Y-1);
M2(1:2:end,1:2:end) = M;

M2(2:2:end,1:2:end) = M(1:end-1,:) & M(2:end,:);
M2(1:2:end,2:2:end) = M(:,1:end-1) & M(:,2:end);

M2(2:2:end,2:2:end) = (M(1:end-1,1:end-1) & M(2:end,2:end)) | ...
    (M(2:end,1:end-1) & M(1:end-1,2:end));

% thin objects to lines: remove pixels so that an object without holes shrinks
% to a minimally connected stroke, and an object with holes shrinks to a
% connected ring halfway between each hole and the outer boundary.
BT = bwmorph(M2,'thin',Inf);

end % end of bwthinupsample