--- /dev/null
+## -*- texinfo -*-
+## @deftypefn {Function File} @var{M} = colorgradient(@var{C}, @var{w}, @var{n})
+## Define a colour map which smoothly traverses the given colors.
+## @var{C} contains the colours, one row per r,g,b value.
+## @var{w}(i) is the relative length of the transition from colour i to colour i+1
+## in the entire gradient. The default is ones(rows(C)-1,1).
+## n is the length of the colour map. The default is rows(colormap).
+##
+## E.g.,
+## @example
+## colorgradient([0,0,1; 1,1,0; 1,0,0]) # blue -> yellow -> red
+## x = linspace(0,1,200);
+## imagesc(x(:,ones(30,1)))';
+## @end example
+## @end deftypefn
+
+## This program is granted to the public domain.
+## Author: Paul Kienzle <pkienzle@users.sf.net>
+
+function ret = colorgradient(C,w,n)
+ if nargin < 1 || nargin > 3
+ usage("M = colorgradient(C,w,n)")
+ endif
+
+ if nargin == 1
+ n = rows(colormap);
+ w = ones(length(C)-1,1);
+ elseif nargin == 2
+ if (length(w) == 1)
+ n = w;
+ w = ones(rows(C)-1,1);
+ else
+ n = rows(colormap);
+ endif
+ endif
+
+ if (length(w)+1 != rows(C))
+ error("must have one weight for each color interval");
+ endif
+
+ w = 1+round((n-1)*cumsum([0;w(:)])/sum(w));
+ map = zeros(n,3);
+ for i=1:length(w)-1
+ if (w(i) != w(i+1))
+ map(w(i):w(i+1),1) = linspace(C(i,1),C(i+1,1),w(i+1)-w(i)+1)';
+ map(w(i):w(i+1),2) = linspace(C(i,2),C(i+1,2),w(i+1)-w(i)+1)';
+ map(w(i):w(i+1),3) = linspace(C(i,3),C(i+1,3),w(i+1)-w(i)+1)';
+ endif
+ endfor
+
+ if nargout == 0
+ colormap(map);
+ else
+ ret = map;
+ endif
+endfunction