/// 
        /// Convex Hull compute.        /// 
        /// The source image points.        ///         ///         private static void ConvexhullCompute(ref Point[] srcPoints,ref List
     
      startPoints,  ref List
      
        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;                }            }        }