MATLAB: Draw a circle and measure the white pixels area inside

circle area

Hello everyone, a binary image is obtained. The work is to draw concentric cirles in the image and calculate the area of the white pixels in each circle. The objective is to get a curve.

I attached an image as an example.

Best Answer

You can construct a distance-squared matrix once. Then you can

sum(bsxfun(@le, distance_squared_matrix(:), radius_row_vector.^2))

to get the counts.

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MATLAB: For the ‘regionprops’ function

Ellipses (actual ones) are always symmetric along both the major and minor axes, so they have a well defined origin which is at their centroid.

If you have partial ellipses instead of full ellipses then the centroid of the region will not generally match the origin of the ellipse.

MATLAB: Delete part of an image

[m,n]=size(oldImage);
x=(1:n); 
y=(1:m).';
mask = (x-innerCenterX).^2+(y-innerCenterY).^2>=innerRadius^2 & ...
       (x-outerCenterX).^2+(y-outerCenterY).^2<=outerRadius^2 ;
       
newImage=oldImage.*mask;

Best Answer

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MATLAB: For the ‘regionprops’ function

MATLAB: Delete part of an image

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