pixels inside circle

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thoraya 2012-5-21

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https://ww2.mathworks.cn/matlabcentral/answers/38954-pixels-inside-circle

评论： Image Analyst 2018-5-4

hi; i need to find pixel coordinates inside a given circle C which is defined by its center position (x , y ) and its radius r. then i need also to find pixel coordinates located at the border of this circle knowing that the width of border is set at 1 or 2 pixels.

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Answer 1

Image Analyst 2012-5-21

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https://ww2.mathworks.cn/matlabcentral/answers/38954-pixels-inside-circle#answer_48497

Have you tried the code in the FAQ: http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F It should be just slight modifications, if any, to get what you want.

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Shaban Sikander 2018-5-4

How to find the black pixels inside a specific circle?

Image Analyst 2018-5-4

在 MATLAB Online 中打开

What does "find" mean to you?

To get a binary image with the black pixels indicated as "true", do

blackPixelMask = grayImage == 0; % Map of all black pixels.
blackPixelMask = blackPixelMask & circleMask; % Erase those outside the circle mask.

To count the number of black pixels, do this:

Make a circle mask, like the FAQ shows you. Then count the black pixels:

pixelsInCircleMask = grayImage(circleMask);
numBlackPixels = sum(pixelsInCircleMask)

Otherwise you'll have to give a precise definition of what the word "find" means to you in this context, because it's ambiguous. I don't know what it means to you.

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