contourPropagate.m

function newPs=contourPropagate(Ps,shrinkRate,sz)

nPoints = 20;
lengthCanSkip = 12;

if(shrinkRate>lengthCanSkip)
    error('shrink too much');
end
% if(shrinkRate>1 || shrinkRate<0)
%     error('incorrect shrink rate');
% elseif(shrinkRate>0.5)
%     shrinkRate = 1-shrinkRate;
% end
    
skipIdx=[];

for i=1:1:numel(Ps)
    
    if(Ps{i}.length<lengthCanSkip)
        skipIdx=cat(1,skipIdx,i);
        continue;
    end
    
    P=Ps{i}.pts;
    
    O(:,1)=interp(P(:,1),10,4);
    O(:,2)=interp(P(:,2),10,4);
    
    
    % Calculate distance between points
    dis=[0;cumsum(sqrt(sum((O(2:end,:)-O(1:end-1,:)).^2,2)))];

    % Resample to make uniform points
    K=zeros(nPoints,2);
    K(:,1) = interp1(dis,O(:,1),linspace(shrinkRate,dis(end)-shrinkRate,nPoints));
    K(:,2) = interp1(dis,O(:,2),linspace(shrinkRate,dis(end)-shrinkRate,nPoints));
    %K(:,1) = interp1(dis,O(:,1),linspace(dis(end)*shrinkRate,dis(end)*(1-shrinkRate),nPoints));
    %K(:,2) = interp1(dis,O(:,2),linspace(dis(end)*shrinkRate,dis(end)*(1-shrinkRate),nPoints));
    
    % Clamp contour to boundary
    K(:,1)=min(max(K(:,1),1),sz(1));
    K(:,2)=min(max(K(:,2),1),sz(2));
    
    t=Ps{i}.thickness;
    %len = Ps{i}.length;
    %len = Ps{i}.targetLength ;
    
    if(isCloseToBoundary(K,sz(1),sz(2)))
        if( Ps{i}.targetLength <0 )
            len = -1;
            cl = Ps{i}.copyLength;
        else
            len = -1;
            cl = Ps{i}.copyLength;
        end
    else
        if(Ps{i}.targetLength<0)
            if(Ps{i}.copyLength==0)
                len = Ps{i}.length;
                cl = Ps{i}.length;
            else
                len = Ps{i}.copyLength;
                cl = len;
            end
        else
            len = Ps{i}.targetLength;
            cl = Ps{i}.copyLength;
        end
    end
    
    Ps{i}=struct('pts',K,'thickness',t,'length',0,'targetLength',len,'copyLength',cl,...
    'strip1',[],'strip2',[],'region',[],'intensity',[],'normvec',[]);
end

if(~isempty(skipIdx))
    numCell=numel(Ps)-numel(skipIdx);
    newPs=cell(1,numCell);
    idx = setdiff(1:1:numel(Ps), skipIdx);
    for i=1:1:numCell
        newPs{i}=Ps{idx(i)};
    end
else
    newPs = Ps;
end