C#图像处理之图像均值方差计算的方法

//本函数均是基于RGB颜色空间计算
//定义图像均值函数（RGB空间）
public double AnBitmap(Bitmap a)
{
  double V = 0;
  Rectangle rect = new Rectangle(0, 0, a.Width, a.Height);
  System.Drawing.Imaging.BitmapData bmpData = a.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadWrite, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
  unsafe
  {
   byte* pIn = (byte*)bmpData.Scan0.ToPointer();
   byte* P;
   int R, G, B;
   double meanvalue = 0, sum = 0; 
   int stride = bmpData.Stride;
   for (int y = 0; y < a.Height; y++)
   {
     for (int x = 0; x < a.Width; x++)
     {
     P = pIn;
     B = P[0];
     G = P[1];
     R = P[2];
     sum += B * 0.114 + G * 0.587 + R * 0.299;
     pIn += 3;
     }
     pIn += stride - a.Width * 3;
   }
   meanvalue = sum / (a.Width * a.Height);
   V = meanvalue;
  }
  a.UnlockBits(bmpData);
  return V;  //返回图像均值V
}
//定义图像统计方差函数（RGB空间）
public double AnCONBitmap(Bitmap a,double meanvalue)
{
  double V = 0;
  Rectangle rect = new Rectangle(0, 0, a.Width, a.Height);
  System.Drawing.Imaging.BitmapData bmpData = a.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadWrite, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
  unsafe
  {
   byte* pIn = (byte*)bmpData.Scan0.ToPointer();
   byte* P;
   int R, G, B;
   double conv = 0, sum = 0;
   int stride = bmpData.Stride;
   for (int y = 0; y < a.Height; y++)
   {
     for (int x = 0; x < a.Width; x++)
     {
     P = pIn;
     B = P[0];
     G = P[1];
     R = P[2];
     sum += (B * 0.114 + G * 0.587 + R * 0.299 - meanvalue) * (B * 0.114 + G * 0.587 + R * 0.299 - meanvalue);
     pIn += 3;
     }
     pIn += stride - a.Width * 3;
    }
    conv = sum / (a.Width * a.Height-1);
   V = conv;
  }
  a.UnlockBits(bmpData);
  return V;  //返回图像方差V
}