function radius = MakeRadiusMat(nx,ny,centerx,centery)
% radius = MakeRadiusMat(nx,ny,centerx,[centery])
%
% Return an n by n matrix whose entries are the
% radial distance in pixels from the center pixel.
%
% This matrix is a useful thing to pre-compute for
% performing certain 2D image processing operations.
%
% The no-loop algorithm is due to Stan Klein.
%
% 7/11/94 dhb Slick version.
% Argument re-write for backward compatibility
if (nargin == 3)
centery = centerx;
end
% Create an ny by nx matrix. Each row is identical and
% contains the square of its x coordinate relative to
% the center.
x = (1:nx) - centerx;
Mx = ones(ny,1)*(x.^2);
% Create an ny by nx matrix. Each column is identical and
% contains the square of its y coordinate relative to
% the center.
y = (1:ny)' - centery;
My = (y.^2)*ones(1,nx);
% Form the desired matrix as
radius = sqrt(Mx + My);