Asp.net(C#)给图片加上水印效果

下面的代码中，加文字水印和加图片水印的代码不能共存
我是为了方便显示才写在一块的

    private void Btn_Upload_Click(object sender, System.EventArgs e)

        

{

            if(UploadFile.PostedFile.FileName.Trim()!="")

            

{

                //上传文件

                string extension = Path.GetExtension(UploadFile.PostedFile.FileName).ToUpper();

                string fileName = DateTime.Now.Year.ToString() + DateTime.Now.Month.ToString() + DateTime.Now.Day.ToString() + DateTime.Now.Hour.ToString() + DateTime.Now.Minute.ToString() + DateTime.Now.Second.ToString();

                string path = Server.MapPath(".") + "/UploadFile/" + fileName + extension;

                UploadFile.PostedFile.SaveAs(path);

                //加文字水印，注意，这里的代码和以下加图片水印的代码不能共存

                System.Drawing.Image image = System.Drawing.Image.FromFile(path);

                Graphics g = Graphics.FromImage(image);

                g.DrawImage(image, 0, 0, image.Width, image.Height);

                Font f = new Font("Verdana", 32);

                Brush b = new SolidBrush(Color.White);

                string addText = AddText.Value.Trim();

                g.DrawString(addText, f, b, 10, 10);

                g.Dispose();

                //加图片水印

                System.Drawing.Image image = System.Drawing.Image.FromFile(path);

                System.Drawing.Image copyImage = System.Drawing.Image.FromFile( Server.MapPath(".") + "/Alex.gif");

                Graphics g = Graphics.FromImage(image);

                g.DrawImage(copyImage, new Rectangle(image.Width-copyImage.Width, image.Height-copyImage.Height, copyImage.Width, copyImage.Height), 0, 0, copyImage.Width, copyImage.Height, GraphicsUnit.Pixel);

                g.Dispose();

                //保存加水印过后的图片,删除原始图片

                string newPath = Server.MapPath(".") + "/UploadFile/" + fileName + "_new" + extension;

                image.Save(newPath);

                image.Dispose();

                if(File.Exists(path))

                

{

                    File.Delete(path);

                }

                Response.Redirect(newPath);

            }

        }

//加图片水印
System.Drawing.Image image = System.Drawing.Image.FromFile(path);
System.Drawing.Image copyImage = System.Drawing.Image.FromFile(@"G:\Documents and Settings\Administrator\桌面\桌面图片\500_XrN4fq31.jpg");
//设置颜色矩阵
int lucencyPercent = 25;
float[][] matrixItems ={
new float[] {1, 0, 0, 0, 0},
new float[] {0, 1, 0, 0, 0},
new float[] {0, 0, 1, 0, 0},
new float[] {0, 0, 0, (float)lucencyPercent/100f, 0},
new float[] {0, 0, 0, 0, 1}};

ColorMatrix colorMatrix = new ColorMatrix(matrixItems);
ImageAttributes imgAttr = new ImageAttributes();
imgAttr.SetColorMatrix(colorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
//绘制阴影图像
Graphics g = Graphics.FromImage(image);
g.DrawImage(copyImage, new Rectangle(image.Width - copyImage.Width, image.Height - copyImage.Height, copyImage.Width, copyImage.Height), 0, 0, copyImage.Width, copyImage.Height, GraphicsUnit.Pixel, imgAttr);
g.Dispose();