指数函数返回零

Question

我正在尝试绘制在下面的纸质链接中流动的指数函数的值，但是，它们始终为零。我正在尝试绘制纸张中显示的灰色图像。你对此有何建议？谢谢

http://i.stack.imgur.com/2KyvO.png http://i.stack.imgur.com/pPend.png

Bitmap bm = (Bitmap)pictureBox1.Image;
            Bitmap bmp = new Bitmap(pictureBox1.Image.Width, pictureBox1.Image.Height);
            Color color = new Color();
            double Cb,Cr,r,g,b,R,G,B; 
            double CbMean = 156.56;//150.3179;
            double CrMean = 117.43;//117.1057;
            double K1 = 160.13;
            double K2 = 12.143;
            double K3 = 12.143;
            double K4 = 299.46;

            for (int i = 0; i < pictureBox1.Width; i++)
            {
                for (int j = 0; j < pictureBox1.Height; j++)
                {

                    color = bm.GetPixel(i, j);
                    R = Convert.ToDouble(color.R);
                    G = Convert.ToDouble(color.G);
                    B = Convert.ToDouble(color.B);
                    if (R != 0 && G != 0 && B != 0)
                    {
                        r = R / (R + G + B);
                        g = G / (R + G + B);
                        b = B / (R + G + B);
                        Cb = (-0.169 * r - 0.331 * g + 0.500 * b);
                        Cr = (0.500 * r - 0.418 * g - 0.082 * b);
                        Cb -= CbMean;
                        Cr -= CrMean;
                        double CbDist = (K1 * Cb) + (K3 * Cr);
                        double CrDist = (K2 * Cb) + (K4 * Cr);
                        double CbDist1 = (-0.5 * Cb) + (-0.5 * Cr);
                        double dist = CbDist + CrDist;
                        double dist1 = CrDist1;
                        double gmm = Math.Exp(dist * dist1); //<-------zero
                        int luma = (int)((gmm * 0.3) + (gmm * 0.59) + (gmm * 0.11));
                        bmp.SetPixel(i, j, Color.FromArgb(luma, luma, luma));
                    }
                }
            }