/// <summary>

        /// Convex Hull compute.

        /// </summary>

        /// <param name="points">The source image points.</param>

        /// <param name="startPoints"></param>

        /// <param name="endPoints"></param>

        private static void ConvexhullCompute(ref Point[] srcPoints,ref List<Point>startPoints,  ref List<Point> endPoints)

        {

            Point start;

            Point end;

            double a = 0, b = 0;

            int signa = 0, signb = 0;

            int max = srcPoints.Length;

            double temp = 0.0;

            int t = 0;

            double tx = 0.0;

            for (int i = 0; i < max; i++)

            {

                start = srcPoints[i];

                for (int k = i + 1; k < max; k++)

                {

                    end = srcPoints[k];

                    if (start.X == end.X)

                    {

                        for (int j = 0; j < max; j++)

                        {

                            if ((!(signa > 0 && signb > 0)) && (j != i && j != k))

                            {

                                t = srcPoints[j].X;

                                if (t > start.X)

                                    signa++;

                                if (t < start.X)

                                    signb++;

                            }

                        }

                    }

                    else

                    {

                        a = (double)(end.Y - start.Y) / (double)(end.X - start.X);

                        b = (double)start.Y - (double)start.X * a;

                        for (int j = 0; j < max; j++)

                        {

                            if ((!(signa > 0 && signb > 0)) && (j != i && j != k))

                            {

                                temp = a * (double)srcPoints[j].X + b;

                                tx = (double)srcPoints[j].Y;

                                if (temp > tx)

                                    signa++;

                                if (temp < tx)

                                    signb++;

                            }

                        }

                    }

                    if (signa * signb == 0)

                    {

                        startPoints.Add(start);

                        endPoints.Add(end);

                    }

                    signb = 0;

                    signa = 0;

                }

            }

        }