Save the circle periphery after detecting the circle

Hello,

I have an image of three circles and I use regionprops() to detect them. I find the radii and centers of the circles, but that is not enough. To illustrate my circles I use viscircles(), but I would like to save the periphery of the circles for later use. I cannot see that regionprops() let me find this property of the circles, and I would like some tips or solution on this problem.

Regards, Katrine

[Ameer Hamza]

regionprops already gives the center and radius of the circle? How else do you want to save the periphery?

[KatherineL]

I would like to save all the points on the periphery which I want to use later. For instance save the coordinates of the circle viscircles() draw and use them.

Answer 1

[Ameer Hamza]

You can calculate the coordinates on the periphery of a circle given the center and radius using these equations

center = [1 2];
radius = 1;

theta = linspace(0, 2*pi, 100);
x = radius*cos(theta);
y = radius*sin(theta);

plot(x,y);

[KatherineL]

Thank you - I got what I needed out from ConvexHull in regionprops().

Answer 2

[Image Analyst]

Try bwboundaries:

boundaries = bwboundaries(binaryImage);
% Plot them.
hold on;
for k = 1 : length(boundaries)
    thisBoundary = boundaries{k};
    x = thisBoundary(:, 2);
    y = thisBoundary(:, 1);
    plot(x, y, 'r-', 'LineWidth', 2);
end

[KatherineL]

Thank you - I got what I needed out from ConvexHull in regionprops().