Interpolation

        //Linear interpolation of a 2D double array        
        private double[,] Interpolate(double[,] matrix, int dim)
        {
            double[,] result = new double[dim, dim];
            double sf = (double)(matrix.GetLength(0) - 1) / (double)(dim - 1d);

            for (int x = 0; x < dim; x++)
            {
                for (int y = 0; y < dim; y++)
                {
                    double oldX = sf * x;
                    double oldY = sf * y;

                    double q12 = matrix[(int)Math.Floor(oldX), (int)Math.Floor(oldY)];    //Oben links
                    double q22 = matrix[(int)Math.Ceiling(oldX), (int)Math.Floor(oldY)];  //Oben rechts
                    double q11 = matrix[(int)Math.Floor(oldX), (int)Math.Ceiling(oldY)];  //Unten links
                    double q21 = matrix[(int)Math.Ceiling(oldX), (int)Math.Ceiling(oldY)];//Unten rechts

                    double x1 = Math.Floor(oldX); //Links
                    double x2 = Math.Ceiling(oldX); //Rechts
                    double y2 = Math.Floor(oldY); //Oben
                    double y1 = Math.Ceiling(oldY); //Unten

                    double x0 = (x2 - oldX);
                    double y0 = (y1 - oldY);

                    double newValue = q11 * (1d - x0) * (1d - y0) +
                        q21 * x0 * (1d - y0) +
                        q12 * y0 * (1d - x0) +
                        q22 * x0 * y0;

                    result[x, y] = newValue;
                }
            }

            return result;
        }