Colour mapping system

A method for computing the output values of a first series of input points, given the output values of a second series of input points is disclosed. The method comprises, for each input point of the first series forming a weighted distance measure, for each of the second series of input points, derived from the absolute distance between the first series input point and the second series input point. Next, an error measure function is determined including a summation over each of the second series of input points, of an absolute error between a proposed line or curve and the output value of the second series of points, weighted by the weighted distance measure. The error measure function is then substantially minimized to produce a finalized line or curve. The finalized line or curve is then used to derive an output value at the first series point.