รบกวนพี่ ๆ ครับ สอบถามเรื่อง GetPixel บน Asp.net ครับ ทำยังไง

Bitmap bitmap = new Bitmap(Server.MapPath("d:xxx.jpg")); 
    MemoryStream memStream = new MemoryStream(); 

// generate image 

// Create a graphics object for drawing. 
Graphics g = Graphics.FromImage(bitmap); 
g.SmoothingMode = SmoothingMode.AntiAlias; 
 
 int width = bitmap.Width; 
 int height = bitmap.Height; 
 
 string familyName = "Tahoma"; 
 string text = Request.Params["Text"]; 
 
 // get a rectangle on his shirt 
 Rectangle rect = new Rectangle(150, 216, 210, 135); 
 
 // Set up the text font. 
 Font font; 
 font = new Font(familyName, 16F, FontStyle.Regular); 
 
 // Set up the text format. 
 StringFormat format = new StringFormat(); 
 format.Alignment = StringAlignment.Center; 
 format.LineAlignment = StringAlignment.Center; 
 
 // Create a path using the text and warp it to fit over his contour 
 GraphicsPath path = new GraphicsPath(); 
 path.AddString(text, font.FontFamily, (int) font.Style, font.Size, rect, format); 
 
 PointF[] points = 
 { 
 new PointF(rect.X - 10, rect.Y - 8), 
 new PointF(rect.X + rect.Width - 20, rect.Y + 4), 
 new PointF(rect.X - 8, rect.Y + rect.Height - 15), 
 new PointF(rect.X + rect.Width - 10, rect.Y + rect.Height + 4) 
 }; 
 Matrix matrix = new Matrix(); 
 matrix.Translate(0F, 0F); 
 path.Warp(points, rect, matrix, WarpMode.Perspective, 0F); 
 
 // Draw the text. 
 HatchBrush hatchBrush = new HatchBrush( 
 HatchStyle.LargeConfetti, 
 Color.LightGray, 
 Color.DarkGray); 
 
 g.FillPath(hatchBrush, path); 
 
 Response.Clear(); 
 Response.ContentType="image/jpeg"; 
 bitmap.Save(memStream, ImageFormat.Jpeg); 
 memStream.WriteTo(Response.OutputStream); 
 
 // Clean up. 
 font.Dispose(); 
 hatchBrush.Dispose(); 
 g.Dispose(); 
 bitmap.Dispose();