asp.net 加水印后不清晰 求解决办法

[ytdiary]

 protected void Button1_Click(object sender, EventArgs e)
    {
        // 根据选中状态初始化值
        float pos_t_x = 390.0f;
        float pos_t_y = 132.0f;
        float pos_b_x = 980.0f;
        float pos_b_y = 363.0f;

        if (RadioButton2.Checked == true)
        {
            pos_t_x = 430;
            pos_t_y = 125;
            pos_b_x = 970;
            pos_b_y = 380;
        }

        if (RadioButton3.Checked == true)
        {
            pos_t_x = 75;
            pos_t_y = 143;
            pos_b_x = 680;
            pos_b_y = 380;
        }

        string Filename =string.Empty;
        string file = Server.MapPath("") + "\\" + Label1.Text.Replace("/", "\\");

        file = file.Replace("image", "card_bg");
        file = file.Replace("_all", "");
        
        System.Text.StringBuilder sb = new System.Text.StringBuilder();
        sb.Append(DateTime.Now.Year.ToString());
        sb.Append(DateTime.Now.Month.ToString());
        sb.Append(DateTime.Now.Day.ToString());
        sb.Append(DateTime.Now.Hour.ToString());
        sb.Append(DateTime.Now.Minute.ToString());
        sb.Append(DateTime.Now.Second.ToString());
        sb.Append(".jpg");
        
        Filename = sb.ToString();

        //生成缩略图
        //原始图片名称
        //生成高质量图片名称
        string strFile = Server.MapPath("~") + "/card/card_" + Filename;

        //从文件获取图片对象
        //System.Drawing.Image image = System.Drawing.Image.FromStream(hpf.InputStream, true);
        System.Drawing.Image image = System.Drawing.Image.FromFile(@file);

        System.Drawing.Image bitmap = new System.Drawing.Bitmap(1024, 634);  //新建bmp图片
        System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);  //新建画板
        g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;  //制定高质量插值法
        g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;   //设置高质量、低速度呈现平滑程度
        g.Clear(System.Drawing.Color.White);    //清空画布
        //在制定位置画图
        g.DrawImage(image, new System.Drawing.Rectangle(0, 0, bitmap.Width, bitmap.Height), new System.Drawing.Rectangle(0, 0, image.Width, image.Height), System.Drawing.GraphicsUnit.Pixel);
        

        int fontsize = 20; // 文字大小


        // 抬头
        //文字水印
        System.Drawing.Graphics testGrahpics = System.Drawing.Graphics.FromImage(bitmap);


        System.Drawing.Text.PrivateFontCollection pfc = new System.Drawing.Text.PrivateFontCollection();
        string fontpath = Server.MapPath("font/font.ttf");//相对于虚拟目录的字体文件路径
        pfc.AddFontFile(fontpath);

        System.Drawing.Font font = new System.Drawing.Font(pfc.Families[0], fontsize);

        System.Drawing.Brush brush = new System.Drawing.SolidBrush(ColorTranslator.FromHtml("#E0DEDD"));

        //分行
        string sInput ="尊敬的" +  TextBox3.Text.Trim().ToString() + DropDownList1.SelectedItem.Text.ToString() + "：";    //获取输入的水印文字

        testGrahpics.DrawString(sInput, font, brush, pos_t_x, pos_t_y);

        fontsize = 14;

        // 写落尾---------------------------------------------------------------


        testGrahpics = System.Drawing.Graphics.FromImage(bitmap);
        font = new System.Drawing.Font(pfc.Families[0], fontsize);
        sInput = TextBox4.Text.Trim().ToString() + "致";    //获取输入的水印文字


        // 为了保证落尾右侧对其，需要重新计算其X初始坐标
        pos_b_x = pos_b_x - (sInput.Length) *(5.0f +  (float) fontsize);

        testGrahpics.DrawString(sInput, font, brush, pos_b_x, pos_b_y);
        
        testGrahpics.Dispose();
        //保存缩略图c
        try
        {
            bitmap.Save(strFile, System.Drawing.Imaging.ImageFormat.Jpeg);
        }
        catch (Exception ex)
        {
            Response.Write("保存缩略图失败" + ex.Message);
        }
        //释放资源
        g.Dispose();
        bitmap.Dispose();
        image.Dispose();
        Image1.ImageUrl = "/card/card_" + Filename;
        Image1.Visible = true;
        HyperLink1.NavigateUrl = "/card/card_" + Filename;
        }

假的水印在文字周围有水渍一样的东西 求解决办法 ，
还有这个是在读取是损坏了还是在保存时损坏的，求各位大神指点啊

[全局变量]

一把水印图变成高分辨率的清晰图片，
System.Drawing.Image bitmap = new System.Drawing.Bitmap(1024, 634); //新建bmp图片
缩小它，或变成水印的分辨率。

说白了就是分辨率的问题

[ytdiary]

谢谢

但是添加水印后图片大小不能改啊。。。。
或者考虑其他实现方式也可以

[wuyq11]

高质量
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
System.Drawing.Imaging.ImageCodecInfo codec = System.Drawing.Imaging.ImageCodecInfo.GetImageEncoders()[1]; System.Drawing.Imaging.EncoderParameters eParams = new System.Drawing.Imaging.EncoderParameters(1);
eParams.Param[0] = new System.Drawing.Imaging.EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 100L);

[ytdiary]

3Q 不解决问题啊

我用png格式了 会好点