function cmap = cyanred(m, k)
%CYANRED    Cyan-black-red colormap
%  cyanred(m,k) gives a cyan-grey-red colormap where the grey-level in
%  the middle is k
%
%  cyanred(m) returns an m-by-3 matrix containing the colormap.
%  cyanred, by itself, is the same length as the current figure's
%  colormap (if no figure exists, MATLAB creates one).
%  The default m for MATLAB colormaps appears to be 64, but
%  something like 256 is visually smoother.
%
%  colormap(cyanred) changes the current figure's colormap.

%  Ged Ridgway 2006

if nargin < 1
    m = size(get(gcf,'colormap'),1);
end
if nargin < 2
    k = 0; % default to black
end

% centre of colormap
c = (m+1)/2;
% lengths of smaller and larger parts (equal for even m)
a = floor(c)-1; b = m-a;

% red, green, blue
r = [k*ones(1, a) linspace(k, 1, b)];
g = [linspace(1, k, b) k*ones(1, a)];
b = g;

cmap = [r' g' b'];