% composite.m                                               Steve Mann
%
% like chnan except changes NaNs to a second image.
% 
% Example: C = composite(A,B);  % anywhere A=NaN, you see B instead

function C = matrixversionofchnan(A,B);

if nargin < 2
  error('composite: you must specify 2 input images')
end%if

Amin=min2nan(A);
Aextended=chnan(A,Amin-1);
whereisNaN=Amin-min(Aextended,ones(size(A))*Amin); % 1 where image is NaN
C=(1-whereisNaN).*Aextended + whereisNaN.*B;