Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / image-1.0.15 / colorgradient.m

diff --git a/octave_packages/image-1.0.15/colorgradient.m b/octave_packages/image-1.0.15/colorgradient.m
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+## -*- 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