how to draw a circle in an image?

Question

ajeet verma 2017-3-1

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/327438-how-to-draw-a-circle-in-an-image

回答： Image Analyst 2017-3-1

采纳的回答： Jan

i want to draw a circle on an image using this equation x^2+y^2=r

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Jan 2017-3-1

编辑：Jan 2017-3-1

According to this formula, the circle is a line with an infinitesimal width, such that it is invisible on the screen. Do you want to draw a disc? Do you mean r^2?

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Answer 1

Jan 2017-3-1

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/327438-how-to-draw-a-circle-in-an-image#answer_256813

在 MATLAB Online 中打开

img   = rand(100, 100, 3) * 0.2;  % Test data
value = bsxfun(@plus, ((1:100) - 50) .^ 2, ((1:100).' - 50) .^ 2);
r     = 30;
mask  = value < (r + 1)^2 & value > (r - 1)^2;
mask3 = cat(3, mask, mask, mask);
img(mask3) = 1.0;
image(img);