function [b2] = make_noisy (b,a,w)

% Takes a clean 0-1 barcode signal b and noises it up.

% Constants.
multiplier = 8;  % how much longer to make the barcode

% Resample barcode at more points.
[temp,N] = size(b);
b1 = zeros(temp,multiplier*N);
for i = 1:N
  b1(1+(i-1)*multiplier:i*multiplier) = b(i);
end;

% Convolve with Gaussian.
[temp,N] = size(b1);
if mod(N,2) == 1
  b1 = [b1 0];
end;
[temp,N] = size(b1);
%shift = round(N/2);
%g = a .* exp (- ( ([1:N]-shift)/w).^2);
%h = conv(b1,g);
x = [1:N]./N - 0.5;
g = a.* exp( - (x/w).^2);
h = conv(b1,g);
h = h(N/2+1:3*N/2);

noise = max(h) / 6;

% Add noise.
[M,N] = size(h);
b2 = h + (2*noise) .* (rand([M,N]) - 0.5);