Attempted to access yC(3); index out of bounds because numel(yC)=2. Error in Contour2Area (line 24) s=(xC(2)-x​C(1))(yC(3​)-yC(2))-(​xC(3)-xC(2​))(yC(2)-y​C(1)); Error in test (line 34) [Area,Cent​roid]=Cont​our2Area(c​f);

function [Area,Centroid]=Contour2Area(C)

nC=length(C);
cc=1;j=1;
while cc<nC
    ix(j)=C(2,cc);
    cvec_start(j)=cc+1;
    cc=cc+ix(j)+1;
    j=j+1;
end
%--- find areas Ac and centroid Cxy (special if contour goes outside) ---
for j=1:length(ix)
    xC=C(1,cvec_start(j):cvec_start(j)+ix(j)-1);
    yC=C(2,cvec_start(j):cvec_start(j)+ix(j)-1);
    if ~isempty(find(isnan(xC)))
        if length(xC)>1
            xC(find(isnan(xC)))=(xC(find(isnan(xC))-1)+xC(find(isnan(xC))+1))/2;
            yC(find(isnan(yC)))=(yC(find(isnan(yC))-1)+yC(find(isnan(yC))+1))/2;
        end
    end
    if length(xC)>1
        Ac(j)=polyarea(xC,yC);  % area
        %--- determine clockwise/reverse sign, s
        s=(xC(2)-xC(1))*(yC(3)-yC(2))-(xC(3)-xC(2))*(yC(2)-yC(1));
        s=s/abs(s);
        Cxy(:,j)=s*sum([(xC(1:end-1)+xC(2:end)).*(xC(1:end-1).*yC(2:end)-xC(2:end).*yC(1:end-1));...
                  (yC(1:end-1)+yC(2:end)).*(xC(1:end-1).*yC(2:end)-xC(2:end).*yC(1:end-1))]')'/...
                  6/Ac(j);  % centroid (centre of mass)
        nan0(j)=0;
    else
        Ac(j)=NaN;
        Cxy(:,j)=[NaN;NaN];
        nan0(j)=1;
    end
    %hold on;plot(xC,yC,'r.',Cxy(1,j),Cxy(2,j),'b*'); % plot polygons and centroids
end
%--- Remove NaN contours ---
nanix=find(nan0~=1);
Area=Ac(nanix);
Centroid=Cxy(:,nanix);

%--- Determine relationship between polygons (inside eachother?, parent/child) ---
IN=zeros(length(nanix),length(nanix));
for i=1:length(nanix)
    i0=nanix(i);
    xC=C(1,cvec_start(i0):cvec_start(i0)+ix(i0)-1);
    yC=C(2,cvec_start(i0):cvec_start(i0)+ix(i0)-1);
    for j=i+1:length(nanix)
        j0=nanix(j);
        IN(i,j)=inpolygon(C(1,cvec_start(j0)),C(2,cvec_start(j0)),xC,yC);
    end
end

    if true
      % code
    end

the program is:

   imout=imread(['frame' num2str(25) '.jpg']);
      n = 20;

      % Divide into nxn images
      s1 = [n*ones(1,floor(size(imout,1)/n)) mod(size(imout,1),n)];
      s2 = [n*ones(1,floor(size(imout,2)/n)) mod(size(imout,2),n)];
      C = mat2cell(imout, s1, s2);

      c=1;
      for i=1:size(C,1)
          for j=1:size(C,2)
          x=find(C{i,j});
          if size(x)~=0
              v(c,1)=i;
              v(c,2)=j;
               v(c,3)=sub2ind(size(C),v(c,1),v(c,2));
               c=c+1;
          end

          end

      end

      for i=1:size(v,1)
         cntr=C{v(i,1),v(i,2)};
         cf=contourf(cntr,1);
         [Area,Centroid]=Contour2Area(cf);
         %g(i:size(Area),1)=sub2ind(size(C),v(i,1),v(i,2));
         %g(i:size(Area),2)=Area;
      end

Answer 1

[Image Analyst]

There is no third element of yC. Why do you think there should be? Anyway, this link will definitely help you figure out why yC is not the size you think it should be: http://blogs.mathworks.com/videos/2012/07/03/debugging-in-matlab/

[sassi nizar]

I don't understand where i can make a condition point, at the ligne 24 of contour2area, or just before the ligne 34 in the test?

[Image Analyst]

I haven't gone over the code in detail but I see three condition lines:

while cc<nC
if length(xC)>1  (twice)
if size(x)~=0

Which one are you asking about and why would you want to move it?

[sassi nizar]

i have divided the image into blocks, and i want calculate in each block the area of the present blob. I am asking for the second if length(xC>1)

[Image Analyst]

How are you defining the blob within the block? Are you thresholding the block? Like

binaryImage = thisBlock > someThresholdValue;
thisArea = sum(binaryImage(:));

What does xC represent? What does size(xC) report?

Why are you using contours? Wouldn't image analysis be easier?