加文字型水印

    /// <summary>
    /// 文字水印
    /// </summary>
    /// <param name="imgPath">服务器图片相对路径</param>
    /// <param name="filename">保存文件名</param>
    /// <param name="watermarkText">水印文字</param>
    /// <param name="watermarkStatus">图片水印位置 0=不使用 1=左上 2=中上 3=右上 4=左中  9=右下</param>
    /// <param name="quality">附加水印图片质量,0-100</param>
    /// <param name="fontname">字体</param>
    /// <param name="fontsize">字体大小</param>
    public static void AddImageSignText(string imgPath, string filename, string watermarkText, int watermarkStatus, int quality, string fontname, int fontsize)
    {
        byte[] _ImageBytes = File.ReadAllBytes(HttpContext.Current.Server.MapPath(imgPath));
        Image img = Image.FromStream(new System.IO.MemoryStream(_ImageBytes));
        filename = HttpContext.Current.Server.MapPath(filename);

        Graphics g = Graphics.FromImage(img);
        Font drawFont = new Font(fontname, fontsize, FontStyle.Regular, GraphicsUnit.Pixel);
        SizeF crSize;
        crSize = g.MeasureString(watermarkText, drawFont);

        float xpos = 0;
        float ypos = 0;

        switch (watermarkStatus)
        {
            case 1:
                xpos = (float)img.Width * (float).01;
                ypos = (float)img.Height * (float).01;
                break;
            case 2:
                xpos = ((float)img.Width * (float).50) - (crSize.Width / 2);
                ypos = (float)img.Height * (float).01;
                break;
            case 3:
                xpos = ((float)img.Width * (float).99) - crSize.Width;
                ypos = (float)img.Height * (float).01;
                break;
            case 4:
                xpos = (float)img.Width * (float).01;
                ypos = ((float)img.Height * (float).50) - (crSize.Height / 2);
                break;
            case 5:
                xpos = ((float)img.Width * (float).50) - (crSize.Width / 2);
                ypos = ((float)img.Height * (float).50) - (crSize.Height / 2);
                break;
            case 6:
                xpos = ((float)img.Width * (float).99) - crSize.Width;
                ypos = ((float)img.Height * (float).50) - (crSize.Height / 2);
                break;
            case 7:
                xpos = (float)img.Width * (float).01;
                ypos = ((float)img.Height * (float).99) - crSize.Height;
                break;
            case 8:
                xpos = ((float)img.Width * (float).50) - (crSize.Width / 2);
                ypos = ((float)img.Height * (float).99) - crSize.Height;
                break;
            case 9:
                xpos = ((float)img.Width * (float).99) - crSize.Width;
                ypos = ((float)img.Height * (float).99) - crSize.Height;
                break;
        }

        g.DrawString(watermarkText, drawFont, new SolidBrush(Color.White), xpos + 1, ypos + 1);
        g.DrawString(watermarkText, drawFont, new SolidBrush(Color.Black), xpos, ypos);

        ImageCodecInfo[] codecs = ImageCodecInfo.GetImageEncoders();
        ImageCodecInfo ici = null;
        foreach (ImageCodecInfo codec in codecs)
        {
            if (codec.MimeType.IndexOf("jpeg") > -1)
                ici = codec;
        }
        EncoderParameters encoderParams = new EncoderParameters();
        long[] qualityParam = new long[1];
        if (quality < 0 || quality > 100)
            quality = 80;

        qualityParam[0] = quality;

        EncoderParameter encoderParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qualityParam);
        encoderParams.Param[0] = encoderParam;

        if (ici != null)
            img.Save(filename, ici, encoderParams);
        else
            img.Save(filename);

        g.Dispose();
        img.Dispose();
    }