circle_matrix(image​,radius, center, value, thickness)

This file help to create a circle or ring matrix and also draw circle in gray and color image with different intensity value.
Example 1:-
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a = imread('lena.tif');
center = [50,300];
color = [255,255,0];
Z = circle_matrix(a, 150, center, color, 5);
imshow(Z)
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example 2:-
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image = uint8(255*ones(512));
center = [75, 150];
image1 = circle_matrix(image, 100); % circle with radius 100
image2 = circle_matrix(image, 100, center); % circle with radius 100 at center(75, 150)
image3 = circle_matrix(image, 100, center, 40);
image4 = circle_matrix(image, 100, center, 40, 40);
subplot(221),imshow(image1)
subplot(222),imshow(image2)
subplot(223),imshow(image3)
subplot(224),imshow(image4)
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