c# fast getPixel

using System;
using System.Collections.Generic;
using System.Text;
using System.Drawing;
using System.Drawing.Imaging;

namespace SampleGrabberNET
{
   public unsafe class UnsafeBitmap
   {
       Bitmap bitmap;

 // three elements used for MakeGreyUnsafe
 int width;
 BitmapData bitmapData = null;
 Byte* pBase = null;

 public UnsafeBitmap(Bitmap bitmap)
 {
     this.bitmap = new Bitmap(bitmap);
 }

       public UnsafeBitmap(int width, int height)
       {
           this.bitmap = new Bitmap(width, height, PixelFormat.Format24bppRgb);
       }

 public void Dispose()
 {
     bitmap.Dispose();
 }

 public Bitmap Bitmap
 {
     get
     {
   return(bitmap);
     }
 }

 private Point PixelSize
 {
     get
     {
   GraphicsUnit unit = GraphicsUnit.Pixel;
   RectangleF bounds = bitmap.GetBounds(ref unit);

   return new Point((int) bounds.Width, (int) bounds.Height);
     }
 }

 public void LockBitmap()
 {
     GraphicsUnit unit = GraphicsUnit.Pixel;
     RectangleF boundsF = bitmap.GetBounds(ref unit);
     Rectangle bounds = new Rectangle((int) boundsF.X,
   (int) boundsF.Y,
   (int) boundsF.Width,
   (int) boundsF.Height);

     // Figure out the number of bytes in a row
     // This is rounded up to be a multiple of 4
     // bytes, since a scan line in an image must always be a multiple of 4 bytes
     // in length.
     width = (int) boundsF.Width * sizeof(PixelData);
     if (width % 4 != 0)
     {
   width = 4 * (width / 4 + 1);
     }
     bitmapData =
   bitmap.LockBits(bounds, ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);

     pBase = (Byte*) bitmapData.Scan0.ToPointer();
 }

 public PixelData GetPixel(int x, int y)
 {
           PixelData returnValue = *PixelAt(x, y);
     return returnValue;
 }

       public void SetPixel(int x, int y, PixelData colour)
       {
           PixelData* pixel = PixelAt(x, y);
           *pixel = colour;
       }

 public void UnlockBitmap()
 {
     bitmap.UnlockBits(bitmapData);
     bitmapData = null;
     pBase = null;
 }
       public PixelData* PixelAt(int x, int y)
       {
           return (PixelData*)(pBase + y * width + x * sizeof(PixelData));
       }
   }
   public struct PixelData
   {
       public byte blue;
       public byte green;
       public byte red;
   }
}