# how to obtain the values of a square matrix inside a circular region of image?

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### Accepted Answer

Walter Roberson
on 16 Nov 2013

d = r/sqrt(2);

xcoords = [x-d x+d x+d x-d x-d];

ycoords = [y-d y-d y+d y+d y-d];

line(xcoords, ycoords)

Now what you need to deal with is the rounding to integer coordinates. Rounding towards the center is the safest way. I would need to think more to figure out if there are circumstances under which it might then be possible to get a slightly larger area by extending one pixel further in one direction.

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