deislands2d.m

function cleanimg = deislands2d(img, sizelim)
%
% cleanimg=deislands2d(img,sizelim)
%
% remove isolated islands on a 2D image below speicified size limit
%
% author: Qianqian Fang (q.fang at neu.edu)
%
% input:
%   img: a 2D binary image
%   sizelim: a integer as the maximum pixel size of a isolated region
%
% output:
%   cleanimg: a binary image after removing islands below sizelim
%
% -- this function is part of iso2mesh toolbox (http://iso2mesh.sf.net)
%

img = squeeze(img);
maxisland = -1;
if (nargin == 2)
    maxisland = sizelim;
end

islands = {};

cleanimg = zeros(size(img));
if (sum(img(:)))
    img = imclose(img, strel('disk', 3));
    islands = bwislands(img);
end

if (length(islands))
    % remove small islands of the foreground
    maxblock = -1;
    maxblockid = -1;
    if (maxisland < 0)
        for i = 1:length(islands)
            if (length(islands{i}) > maxblock)
                maxblockid = i;
                maxblock = length(islands{i});
            end
        end
        if (maxblock > 0)
            cleanimg(islands{maxblockid}) = 1;
        end
    else
        for i = 1:length(islands)
            if (length(islands{i}) > maxisland)
                cleanimg(islands{i}) = 1;
            end
        end
    end

    % remote small islands of the background

    cleanimg = imfill(cleanimg, 'holes');
end