The ellipse is outlined, how to fill?

Question

In this tutorial, an ellipse will be outlined. As you can see, a red border will be drawn around. Form such result, how can we fill such surrounded border with white, and the rest of the image as black?

Thanks.

Answer 1

A little Google search with the words fill and Matlab would tell you that there is a function called fill which performs what you want(check here).

In the example, putting it right after the call to plot gives something like the following. I put the whole code for the for-loop:

for k = 1:length(s)
xbar = s(k).Centroid(1);
ybar = s(k).Centroid(2);

a = s(k).MajorAxisLength/2;
b = s(k).MinorAxisLength/2;

theta = pi*s(k).Orientation/180;
R = [ cos(theta)   sin(theta)
     -sin(theta)   cos(theta)];

xy = [a*cosphi; b*sinphi];
xy = R*xy;

x = xy(1,:) + xbar;
y = xy(2,:) + ybar;

plot(x,y,'r','LineWidth',2);

fill(x,y,rand(1,3)) %// Here is the important line.
end

I'll let you discover how you can fill the ellipses with white instead of random colors.