Explanation on how to make a circle

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Kash Costello
Kash Costello 2018-10-31
编辑： dpb 2018-10-31
% Create a logical image of a circle with specified
% diameter, center, and image size.
% First create the image.
imageSizeX = 640;
imageSizeY = 480;
[columnsInImage rowsInImage] = meshgrid(1:imageSizeX, 1:imageSizeY);
% Next create the circle in the image.
centerX = 320;
centerY = 240;
radius = 100;
circlePixels = (rowsInImage - centerY).^2 ...
+ (columnsInImage - centerX).^2 <= radius.^2;
% circlePixels is a 2D "logical" array.
% Now, display it.
image(circlePixels) ;
colormap([0 0 0; 1 1 1]);
title('Binary image of a circle');
Can someone just explain to me this part:
circlePixels = (rowsInImage - centerY).^2 ...
+ (columnsInImage - centerX).^2 <= radius.^2;
I just want to further understand the whole code. If it's not too much, explanation of the whole code will be more appreciated. Thanks a lot!
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Kash Costello
Kash Costello 2018-10-31
Hi there! But this this part: (rowsInImage - centerY).^2? Or the other one for X? Why is it this way?
dpb
dpb 2018-10-31
编辑：dpb 2018-10-31
How do you calculate the radius of a circle with pencil and paper?
Or, more directly, what's the distance to a point from it's origin given x,y coordinates for the point?

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