C#图像伪彩色处理方法

//灰度图转伪彩色图像函数
public Bitmap PGrayToColor(Bitmap src)
{
  try
  {
   Bitmap a = new Bitmap(src);
   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);
   int stride = bmpData.Stride;
   unsafe
   {
     byte* pIn = (byte*)bmpData.Scan0.ToPointer();
     byte* P;
     int R, G, B;
     int temp = 0;
     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];
       temp = (byte)(B * 0.114 + G * 0.587 + R * 0.299);
       if (temp >= 0 && temp <= 63)
       {
        P[2] = 0;
        P[1] = (byte)(254 - 4 * temp);
        P[0] = (byte)255;
       }
       if (temp >= 64 && temp <= 127)
       {
        P[2] = 0;
        P[1] = (byte)(4 * temp - 254);
        P[0] = (byte)(510 - 4 * temp);
       }
       if (temp >= 128 && temp <= 191)
       {
        P[2] = (byte)(4 * temp - 510);
        P[1] = (byte)(255);
        P[0] = (byte)0;
       }
       if (temp >= 192 && temp <= 255)
       {
        P[2] = (byte)255;
        P[1] = (byte)(1022 - 4 * temp);
        P[0] = (byte)0;
       }
       pIn += 3;
     }
     pIn += stride - a.Width * 3;
     }
   }
   a.UnlockBits(bmpData);
   return a;
  }
  catch (Exception e)
  {
   MessageBox.Show(e.Message.ToString());
   return null;
  }
}