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);

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sassi nizar
sassi nizar 2015-11-17
评论： Image Analyst 2015-11-18
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

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回答（1 个）

Image Analyst
Image Analyst 2015-11-17
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/
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sassi nizar
sassi nizar 2015-11-18
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
Image Analyst 2015-11-18
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?

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