asp .net 为图片添加文字水印(内包含有加图片水印的方法) .

在项目中先创建一个Imag_writer 类库

在该类库下分别创建两个枚举类型WaterMarkType (水印的类型)、WaterMarkPosition (水印的位置)。代码如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Imag_writer
{
    /// <summary>
    /// 水印的类型
    /// </summary>
    public enum WaterMarkType
    {
        /// <summary>
        /// 文字水印
        /// </summary>
        TextMark,
        /// <summary>
        /// 图片水印
        /// </summary>
        ImageMark // 暂时只能添加文字水印
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Imag_writer
{
    /// <summary>
    /// 水印的位置
    /// </summary>
    public enum WaterMarkPosition
    {
        /// <summary>
        /// 左上角
        /// </summary>
        WMP_Left_Top,
        /// <summary>
        /// 左下角
        /// </summary>
        WMP_Left_Bottom,
        /// <summary>
        /// 右上角
        /// </summary>
        WMP_Right_Top,
        /// <summary>
        /// 右下角
        /// </summary>
        WMP_Right_Bottom
    }
}

再创建一个ImageWaterMark 类(用来处理图片添加水印的类)，代码如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Collections;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
namespace Imag_writer
{
    //// <summary>
    /// 处理图片的类（包括加水印，生成缩略图）
    /// </summary>
    public class ImageWaterMark
    {
        public ImageWaterMark()
        {
            //
            // TODO: 在此处添加构造函数逻辑
            //
        }
        /// <summary>
        /// 添加水印(分图片水印与文字水印两种)
        /// </summary>
        /// <param name="oldpath">原图片绝对地址</param>
        /// <param name="newpath">新图片放置的绝对地址(不可与原图片名相同)</param>
        /// <param name="wmtType">要添加的水印的类型</param>
        /// <param name="sWaterMarkContent">水印内容，此即为要添加的文字</param>
        public void AddWaterMarkText(string oldpath, string newpath,WaterMarkType wmtType, string sWaterMarkContent)
        {
            try
            {
                Image image = Image.FromFile(oldpath);
                Bitmap b = new Bitmap(image.Width, image.Height,PixelFormat.Format24bppRgb);
                Graphics g = Graphics.FromImage(b);
                g.Clear(Color.White);
                g.SmoothingMode = SmoothingMode.HighQuality;
                g.InterpolationMode = InterpolationMode.High;
                g.DrawImage(image, , , image.Width, image.Height);
                switch (wmtType)
                {
                    /**/
                    /*case WaterMarkType.ImageMark:
                    //图片水印
                    this.addWatermarkImage(g,
                        Page.Server.MapPath(Watermarkimgpath),
                        WatermarkPosition,image.Width,image.Height);
                    break;*/
                    case WaterMarkType.TextMark:
                        //文字水印
                        this.addWatermarkText(g, sWaterMarkContent, "WM_BOTTOM_RIGHT",
                            image.Width, image.Height);
                        break;
                }
                b.Save(newpath);
                b.Dispose();
                image.Dispose();
            }
            catch
            {
                if (File.Exists(oldpath))
                {
                    //File.Delete(oldpath);
                }
            }
            finally
            {
                if (File.Exists(oldpath))
                {
                    // File.Delete(oldpath);
                }
            }
        }

//--------------------------------------------------------------------------------------
        ///  <summary>
        /// 在图片上生成图片水印
        ///  </summary>
        ///  <param name="Path">原服务器图片路径 </param>
        ///  <param name="Path_syp">生成的带图片水印的图片路径 </param>
        ///  <param name="Path_sypf">水印图片路径 </param>
        public void AddWaterPic(string Path, string Path_syp, string Path_sypf)
        {
            Image image = Image.FromFile(Path);
            Image copyImage = Image.FromFile(Path_sypf);
            Graphics g = Graphics.FromImage(image);
            Rectangle rect = new Rectangle(image.Width - copyImage.Width, image.Height - copyImage.Height, copyImage.Width, copyImage.Height);
            g.DrawImage(copyImage, rect, , , copyImage.Width, copyImage.Height, GraphicsUnit.Pixel);
            g.Dispose();
            image.Save(Path_syp);
            image.Dispose();
        }

       // 给图片加水印#region 给图片加水印
        /// <summary>
        /// 添加水印(分图片水印与文字水印两种)
        /// </summary>
        /// <param name="oldpath">原图片绝对地址</param>
        /// <param name="newpath">新图片放置的绝对地址(不可与原图片名相同)</param>
        /// <param name="wmtType">要添加的水印的类型</param>
        /// <param name="sWaterMarkContent">水印内容，若添加文字水印，此即为要添加的文字；
        /// 若要添加图片水印，此为图片的路径(图片水印暂不可用)</param>
        public void addWaterMark(string oldpath, string newpath,
            WaterMarkType wmtType, string sWaterMarkContent)
        {
            try
            {
                Image image = Image.FromFile(oldpath);
                Bitmap b = new Bitmap(image.Width, image.Height,
                    PixelFormat.Format24bppRgb);
                Graphics g = Graphics.FromImage(b);
                g.Clear(Color.White);
                g.SmoothingMode = SmoothingMode.HighQuality;
                g.InterpolationMode = InterpolationMode.High;
                g.DrawImage(image, , , image.Width, image.Height);
                switch (wmtType)
                {
                    /**//*case WaterMarkType.ImageMark:
                        //图片水印
                        this.addWatermarkImage(g,
                            Page.Server.MapPath(Watermarkimgpath),
                            WatermarkPosition,image.Width,image.Height);
                        break;*/
                    case WaterMarkType.TextMark:
                        //文字水印
                        this.addWatermarkText(g, sWaterMarkContent, "WM_BOTTOM_RIGHT",
                            image.Width, image.Height);
                        break;
                }
                b.Save(newpath);
                b.Dispose();
                image.Dispose();
            }
            catch
            {
                if(File.Exists(oldpath))
                {
                    //File.Delete(oldpath);
                }
            }
            finally
            {
                if(File.Exists(oldpath))
                {
                   // File.Delete(oldpath);
                }
            }
        }
        /**//// <summary>
        ///  加水印文字
        /// </summary>
        /// <param name="picture">imge 对象</param>
        /// <param name="_watermarkText">水印文字内容</param>
        /// <param name="_watermarkPosition">水印位置</param>
        /// <param name="_width">被加水印图片的宽</param>
        /// <param name="_height">被加水印图片的高</param>
        private void addWatermarkText(Graphics picture, string _watermarkText,
            string _watermarkPosition, int _width, int _height)
        {
            // 确定水印文字的字体大小
            int[] sizes = new int[]{, , , , , , , , , , , , , , };
            Font crFont = null;
            SizeF crSize = new SizeF();
            for (int i = ;i < sizes.Length; i++)
            {
                crFont = new Font("Arial Black", sizes[i], FontStyle.Bold);
                crSize = picture.MeasureString(_watermarkText, crFont);
                if((ushort)crSize.Width < (ushort)_width)
                {
                    break;
                }
            }
            // 生成水印图片（将文字写到图片中）
            Bitmap floatBmp = new Bitmap((int)crSize.Width + ,
                           (int)crSize.Height + , PixelFormat.Format32bppArgb);
            Graphics fg=Graphics.FromImage(floatBmp);
            PointF pt=new PointF(,);
            // 画阴影文字
            Brush TransparentBrush0 = new SolidBrush(Color.FromArgb(, Color.Black));
            Brush TransparentBrush1 = new SolidBrush(Color.FromArgb(, Color.Black));
            fg.DrawString(_watermarkText,crFont,TransparentBrush0, pt.X, pt.Y + );
            fg.DrawString(_watermarkText,crFont,TransparentBrush0, pt.X + , pt.Y);
            fg.DrawString(_watermarkText,crFont,TransparentBrush1, pt.X + , pt.Y + );
            fg.DrawString(_watermarkText,crFont,TransparentBrush1, pt.X, pt.Y + );
            fg.DrawString(_watermarkText,crFont,TransparentBrush1, pt.X + , pt.Y);
            TransparentBrush0.Dispose();
            TransparentBrush1.Dispose();
            // 画文字
            fg.SmoothingMode=System.Drawing.Drawing2D.SmoothingMode.HighQuality;
            fg.DrawString(_watermarkText,
                crFont, new SolidBrush(Color.White),
                pt.X, pt.Y, StringFormat.GenericDefault);
            // 保存刚才的操作
            fg.Save();
            fg.Dispose();
            // floatBmp.Save("d://WebSite//DIGITALKM//ttt.jpg");
            // 将水印图片加到原图中
            this.addWatermarkImage(
                picture,
                new Bitmap(floatBmp),
                "WM_BOTTOM_RIGHT",
                _width,
                _height);
        }
        /**//// <summary>
        ///  加水印图片
        /// </summary>
        /// <param name="picture">imge 对象</param>
        /// <param name="iTheImage">Image对象（以此图片为水印）</param>
        /// <param name="_watermarkPosition">水印位置</param>
        /// <param name="_width">被加水印图片的宽</param>
        /// <param name="_height">被加水印图片的高</param>
        private void addWatermarkImage( Graphics picture,Image iTheImage,
            string _watermarkPosition,int _width,int _height)
        {
            Image watermark = new Bitmap(iTheImage);

            ImageAttributes imageAttributes = new ImageAttributes();
            ColorMap colorMap = new ColorMap();
            colorMap.OldColor = Color.FromArgb(, , , );
            colorMap.NewColor = Color.FromArgb(, , , );
            ColorMap[] remapTable = {colorMap};
            imageAttributes.SetRemapTable(remapTable, ColorAdjustType.Bitmap);
            float[][] colorMatrixElements = {
                                                new float[] {1.0f, 0.0f, 0.0f, 0.0f, 0.0f},
                                                new float[] {0.0f, 1.0f, 0.0f, 0.0f, 0.0f},
                                                new float[] {0.0f, 0.0f, 1.0f, 0.0f, 0.0f},
                                                new float[] {0.0f, 0.0f, 0.0f, 0.3f, 0.0f},
                                                new float[] {0.0f, 0.0f, 0.0f, 0.0f, 1.0f}
                                            };

            ColorMatrix colorMatrix = new ColorMatrix(colorMatrixElements);

            imageAttributes.SetColorMatrix(colorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
            int xpos = ;
            int ypos = ;
            int WatermarkWidth = ;
            int WatermarkHeight = ;
            double bl = 1d;
            //计算水印图片的比率
            //取背景的1/4宽度来比较
            if ((_width > watermark.Width * ) && (_height > watermark.Height * ))
            {
                bl = ;
            }
            else if ((_width > watermark.Width * ) && (_height<watermark.Height * ))
            {
                bl = Convert.ToDouble(_height / ) / Convert.ToDouble(watermark.Height);

            }
            else if ((_width < watermark.Width * ) && (_height > watermark.Height * ))
            {
                bl = Convert.ToDouble(_width / ) / Convert.ToDouble(watermark.Width);
            }
            else
            {
                if ((_width * watermark.Height) > (_height * watermark.Width))
                {
                    bl = Convert.ToDouble(_height / ) / Convert.ToDouble(watermark.Height);

                }
                else
                {
                    bl = Convert.ToDouble(_width / ) / Convert.ToDouble(watermark.Width);

                }

            }
            WatermarkWidth = Convert.ToInt32(watermark.Width * bl);
            WatermarkHeight = Convert.ToInt32(watermark.Height * bl);
            switch (_watermarkPosition)
            {
                case "WM_TOP_LEFT":
                    xpos = ;
                    ypos = ;
                    break;
                case "WM_TOP_RIGHT":
                    xpos = _width - WatermarkWidth - ;
                    ypos = ;
                    break;
                case "WM_BOTTOM_RIGHT":
                    xpos = _width - WatermarkWidth - ;
                    ypos = _height -WatermarkHeight - ;
                    break;
                case "WM_BOTTOM_LEFT":
                    xpos = ;
                    ypos = _height - WatermarkHeight - ;
                    break;
            }
            picture.DrawImage(
                watermark,
                new Rectangle(xpos, ypos, WatermarkWidth, WatermarkHeight),
                ,
                ,
                watermark.Width,
                watermark.Height,
                GraphicsUnit.Pixel,
                imageAttributes);
            watermark.Dispose();
            imageAttributes.Dispose();
        }
        /**//// <summary>
        ///  加水印图片
        /// </summary>
        /// <param name="picture">imge 对象</param>
        /// <param name="WaterMarkPicPath">水印图片的地址</param>
        /// <param name="_watermarkPosition">水印位置</param>
        /// <param name="_width">被加水印图片的宽</param>
        /// <param name="_height">被加水印图片的高</param>
        private void addWatermarkImage( Graphics picture,string WaterMarkPicPath,
            string _watermarkPosition,int _width,int _height)
        {
            Image watermark = new Bitmap(WaterMarkPicPath);

            this.addWatermarkImage(picture, watermark, _watermarkPosition, _width,
                _height);
        }
        //生成缩略图#region 生成缩略图
        /**//// <summary>
        /// 保存图片
        /// </summary>
        /// <param name="image">Image 对象</param>
        /// <param name="savePath">保存路径</param>
        /// <param name="ici">指定格式的编解码参数</param>
        private void SaveImage(Image image, string savePath, ImageCodecInfo ici)
        {
            //设置 原图片 对象的 EncoderParameters 对象
            EncoderParameters parameters = new EncoderParameters();
            parameters.Param[] = new EncoderParameter(
                System.Drawing.Imaging.Encoder.Quality, ((long) ));
            image.Save(savePath, ici, parameters);
            parameters.Dispose();
        }
        /**//// <summary>
        /// 获取图像编码解码器的所有相关信息
        /// </summary>
        /// <param name="mimeType">包含编码解码器的多用途网际邮件扩充协议 (MIME) 类型的字符串</param>
        /// <returns>返回图像编码解码器的所有相关信息</returns>
        private ImageCodecInfo GetCodecInfo(string mimeType)
        {
            ImageCodecInfo[] CodecInfo = ImageCodecInfo.GetImageEncoders();
            foreach(ImageCodecInfo ici in CodecInfo)
            {
                if(ici.MimeType == mimeType)
                    return ici;
            }
            return null;
        }
        /**//// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="sourceImagePath">原图片路径(相对路径)</param>
        /// <param name="thumbnailImagePath">生成的缩略图路径,如果为空则保存为原图片路径(相对路径)</param>
        /// <param name="thumbnailImageWidth">缩略图的宽度（高度与按源图片比例自动生成）</param>
        public void ToThumbnailImages(
            string SourceImagePath,
            string ThumbnailImagePath,
            int ThumbnailImageWidth)
        {
            Hashtable htmimes = new Hashtable();
            htmimes[".jpeg"] = "image/jpeg";
            htmimes[".jpg"] = "image/jpeg";
            htmimes[".png"] = "image/png";
            htmimes[".tif"] = "image/tiff";
            htmimes[".tiff"] = "image/tiff";
            htmimes[".bmp"] = "image/bmp";
            htmimes[".gif"] = "image/gif";
            // 取得原图片的后缀
            string sExt = SourceImagePath.Substring(
                SourceImagePath.LastIndexOf(".")).ToLower();
            //从 原图片 创建 Image 对象
            Image image = Image.FromFile(SourceImagePath);
            int num = ((ThumbnailImageWidth / ) * );
            int width = image.Width;
            int height = image.Height;
            //计算图片的比例
            if ((((double) width) / ((double) height)) >= 1.3333333333333333f)
            {
                num = ((height * ThumbnailImageWidth) / width);
            }
            else
            {
                ThumbnailImageWidth = ((width * num) / height);
            }
            if ((ThumbnailImageWidth < ) || (num < ))
            {
                return;
            }
            //用指定的大小和格式初始化 Bitmap 类的新实例
            Bitmap bitmap = new Bitmap(ThumbnailImageWidth, num,
                PixelFormat.Format32bppArgb);
            //从指定的 Image 对象创建新 Graphics 对象
            Graphics graphics = Graphics.FromImage(bitmap);
            //清除整个绘图面并以透明背景色填充
            graphics.Clear(Color.Transparent);
            graphics.SmoothingMode = SmoothingMode.HighQuality;
            graphics.InterpolationMode = InterpolationMode.High;
            //在指定位置并且按指定大小绘制 原图片 对象
            graphics.DrawImage(image, new Rectangle(, , ThumbnailImageWidth, num));
            image.Dispose(); 

            try
            {
                //将此 原图片 以指定格式并用指定的编解码参数保存到指定文件
                SaveImage(bitmap, ThumbnailImagePath,
                    GetCodecInfo((string)htmimes[sExt]));
            }
            catch(System.Exception e)
            {
                throw e;
            }
        }
    }
}

最后在客户端调用时的代码如下( 在页面加载时去处理添加图片水印，也可以根据自己的需要去写要某个事件中)：

    protected void Page_Load(object sender, EventArgs e)
    {
        //新的文件名称
        string newfileName = Server.MapPath("img/") + DateTime.Now.Millisecond + "" + DateTime.Now.Second + ".jpg";
        ImageWaterMark iwm = new ImageWaterMark();
        //原图片路径，新图片路径，要添加的水印类型，要添加的文字内容或是水印图片的路径(加图片水印时用到的)
        iwm.addWaterMark(Server.MapPath("img/Chrysanthemum.jpg"), newfileName, WaterMarkType.TextMark, "shiqiang");
    }