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Identical points in the contour

I have a set of 2D points (unordered) forming a closed loop and I would like to count them down to 14 equally spaced points. This is the outline of the kidney in the image. Any ideas?

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One intuitive approach (IMO) is to create an independent variable for x

and y

. Place it at the arc length and interpolate on it.

% close the contour, temporarily
xc = [x(:); x(1)];
yc = [y(:); y(1)];

% current spacing may not be equally spaced
dx = diff(xc);
dy = diff(yc);

% distances between consecutive coordiates
dS = sqrt(dx.^2+dy.^2);
dS = [0; dS];     % including start point

% arc length, going along (around) snake
d = cumsum(dS);  % here is your independent variable
perim = d(end);

Now you have an independent variable, and you can interpolate to create segments N

:



N = 14;
ds = perim / N;
dSi = ds*(0:N).'; %' your NEW independent variable, equally spaced

dSi(end) = dSi(end)-.005; % appease interp1

xi = interp1(d,xc,dSi);
yi = interp1(d,yc,dSi);

xi(end)=[]; yi(end)=[];

Try using imfreehand

:

figure, imshow('cameraman.tif');
h = imfreehand(gca);
xy = h.getPosition; x = xy(:,1); y = xy(:,2);
% run the above solution ...
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Let's say that your contour is defined by an independent x vector and a dependent y vector.

You can get your tried and tested vector x with linspace:

new_x = linspace(min(x),max(x),14); %14 to get 14 equally spaced points


Then use interp1 to get the values ​​of new_y at each point of new_x:

new_y = interp1(x,y,new_x);

There are several interpolation methods - linear by default. See interp1 help for details.

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