Asp.net 上传图片添半透明图片或文字水印的方法（一）

主要用到System.Drawing 命名空间下的相关类，如Brush、Image、Bitmap、Graphics等等类

Image类可以从图片文件创建Image的实例，Bitmap可以从文件也可以从已有的Image对象创建实例，而Graphics类则是封装了对图像的相关操作，可以理解为一个绘图的面板，在这个面板里你可以添加文字，添加背景等等很多常规绘图软件具备的功能。

下面就怎样添加水印做简单的介绍：

为了方便理解我把水印分为文字型的水印以及图片型的水印，它们都派生自WatermarkPainter基类，需要实现基类中的AddWatermark的方法，这个方法是用来具体的绘图用。

WatermarkPainter类如下：

 

using System.Drawing;
using System.IO;
using System.Text;
using System;

namespace Juice.Common.Drawing
{
    /// <summary>
    /// 图片水印绘制器
    /// </summary>
    public abstract class WatermarkPainter : IDisposable
    {
        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="rawImagePath"></param>
        /// <param name="alpha"></param>
        /// <param name="replaceRawImage"></param>
        protected WatermarkPainter(string rawImagePath, int alpha, bool replaceRawImage)
        {
            ImageToBePainted = rawImagePath;
            WatermarkAlpha = alpha;
            ReplaceRawImage = replaceRawImage;
        }

        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="rawImagePath"></param>
        /// <param name="alpha"></param>
        protected WatermarkPainter(string rawImagePath, int alpha)
            : this(rawImagePath, alpha, true)
        { }

        /// <summary>
        /// 为临时存储文件添加的后缀
        /// </summary>
        private string m_TempFileSuffix = ".juice.watermark.temp";

        /// <summary>
        /// 水印的透明度
        /// </summary>
        private int m_WatermarkAlpha;

        /// <summary>
        /// 水印透明度
        /// </summary>
        public int WatermarkAlpha
        {
            get
            {
                if (m_WatermarkAlpha > 255)
                    m_WatermarkAlpha = 255;
                else if (m_WatermarkAlpha < 0)
                    m_WatermarkAlpha = 0;
                return m_WatermarkAlpha;
            }
            set { m_WatermarkAlpha = value; }
        }

        private string m_ImageToBePainted;

        /// <summary>
        /// 添加水印的图片的物理路径
        /// </summary>
        public string ImageToBePainted
        {
            get { return m_ImageToBePainted; }
            set { m_ImageToBePainted = value; }
        }

        private bool m_ReplaceRawImage;

        /// <summary>
        /// 是否用加了水印的图片替换原有的图片
        /// </summary>
        public bool ReplaceRawImage
        {
            get { return m_ReplaceRawImage; }
            set { m_ReplaceRawImage = value; }
        }

        private string m_TempImagePath;

        /// <summary>
        /// 加了水印后的临时储存名称
        /// </summary>
        protected string TempImagePath
        {
            get
            {
                if (string.IsNullOrEmpty(this.m_TempImagePath))
                {
                    StringBuilder s = new StringBuilder(ImageToBePainted);
                    s.Append(this.m_TempFileSuffix);
                    this.m_TempImagePath = s.ToString();
                }
                return m_TempImagePath;
            }
            set { m_TempImagePath = value; }
        }

        /// <summary>
        /// 原始图像
        /// </summary>
        private Image m_RawImage;

        /// <summary>
        /// 为图片添加水印
        /// </summary>
        public void PaintWaterMark()
        {
            if (string.IsNullOrEmpty(ImageToBePainted))
                return;
            if (!System.IO.File.Exists(ImageToBePainted))
                throw new FileNotFoundException(string.Format("file {0} not found.", ImageToBePainted));
            bool succeed;
            if (m_RawImage == null)
                m_RawImage = Image.FromFile(ImageToBePainted);
            ///原始的图片
            using (Bitmap newImage = new Bitmap(m_RawImage.Width, m_RawImage.Height))
            {
                ///创建绘制图片的图面
                using (Graphics g = Graphics.FromImage(newImage))
                {
                    g.DrawImage(m_RawImage, 0, 0, m_RawImage.Width, m_RawImage.Height);
                    ///开始绘制水印
                    succeed = AddWatermark(g, newImage);
                }
                if (succeed)
                    ///将图片保存到临时的文件
                    newImage.Save(TempImagePath);
                if (m_RawImage != null)
                    m_RawImage.Dispose();
            }
            if (succeed && ReplaceRawImage)
            {
                //删除原来的文件
                if (System.IO.File.Exists(ImageToBePainted))
                    System.IO.File.Delete(ImageToBePainted);
                FileInfo info = new FileInfo(TempImagePath);
                if (info.Exists)
                {
                    info.MoveTo(ImageToBePainted);
                }
            }

        }

        /// <summary>
        /// 添加水印，继承类可以用来添加自己的水印
        /// </summary>
        /// <param name="graphics"></param>
        /// <param name="newImage"></param>
        /// <returns></returns>
        protected abstract bool AddWatermark(Graphics graphics, Bitmap newImage);

        #region IDisposable 成员

        public virtual void Dispose()
        {
           
        }

        #endregion
    }
}

而文字型的水印的类是TextWatermarkPainter类

 

using System.Drawing;
using System.IO;
using System.Text;
using System;

namespace Juice.Common.Drawing
{
    /// <summary>
    /// 添加文字水印
    /// </summary>
    public sealed class TextWatermarkPainter : WatermarkPainter
    {
        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="rawImagePath"></param>
        /// <param name="alpha"></param>
        /// <param name="text"></param>
        public TextWatermarkPainter(string rawImagePath, int alpha, string text)
            : base(rawImagePath, alpha)
        {
            WatermarkText = text;
        }

        private Font m_Font;

        /// <summary>
        /// 水印文字的字体
        /// </summary>
        public Font Font
        {
            get
            {
                if (null == m_Font)
                    m_Font = new Font("Arial Black", 14, FontStyle.Bold, GraphicsUnit.Pixel);
                return m_Font;
            }
            set { m_Font = value; }
        }

        private Color m_FontColor;

        /// <summary>
        /// 字体颜色
        /// </summary>
        public Color FontColor
        {
            get
            {
                if (m_FontColor == null)
                    m_FontColor = Color.DarkSeaGreen;
                return m_FontColor;
            }
            set { m_FontColor = value; }
        }

        private string m_WatermarkText;

        /// <summary>
        /// 水印的文字
        /// </summary>
        public string WatermarkText
        {
            get { return m_WatermarkText; }
            set { m_WatermarkText = value; }
        }

        /// <summary>
        /// 实现添加水印的方法
        /// </summary>
        /// <param name="graphics"></param>
        /// <param name="newImage"></param>
        /// <returns></returns>
        protected override bool AddWatermark(Graphics graphics, Bitmap newImage)
        {
            if (string.IsNullOrEmpty(WatermarkText))
                return true;
            using (SolidBrush brush = new SolidBrush(Color.FromArgb(WatermarkAlpha, FontColor.R, FontColor.G, FontColor.B)))
            {
                Font font;
                ///添加文字位置
                PointF f = new PointF();
                float totalWidth = Font.Size * WatermarkText.Length;
                f.X = newImage.Width - totalWidth - 100;
                f.Y = newImage.Height - Font.Height;
                if (f.X < 0)
                {
                    ///自动调整字体的大小
                    float width = newImage.Width / WatermarkText.Length;
                    font = new Font(Font.FontFamily, width, GraphicsUnit.Pixel);
                }
                else
                    font = Font;
                graphics.DrawString(WatermarkText, font, brush, f);
            }
            return true;
        }

        #region IDisposable 成员

        public override void Dispose()
        {
            Font.Dispose();
            base.Dispose();
        }

        #endregion
    }
}

 

下面是对文字型水印的测试：

default.aspx内容如下：

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>无标题页</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        水印文字:<asp:TextBox ID="watermarkTextBox" runat="server"></asp:TextBox><br />
        选择上传图片:<asp:FileUpload ID="FileUpload1" runat="server" Width="189px" />
        <br />
        <asp:Button ID="uploadFileBtn" runat="server" Text="上传图片并且加文字水印"
            onclick="uploadFileBtn_Click" />
        <br />加了水印的图像如下：
        <asp:Image ID="image" runat="server" />
    </div>
    </form>
</body>
</html>

default.aspx.cs代码如下：

using System;
using System.Configuration;
using System.Data;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using Juice.Common.Drawing;
using System.Web.Hosting;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void uploadFileBtn_Click(object sender, EventArgs e)
    {
        if (string.IsNullOrEmpty(this.watermarkTextBox.Text))
            return;
        if (FileUpload1.HasFile)
        {
            string contentType = FileUpload1.PostedFile.ContentType;
            if (contentType.StartsWith("image/"))
            {
                string filePath = Server.MapPath(string.Format("~/{0}", FileUpload1.PostedFile.FileName));
                ///保存文件
                FileUpload1.SaveAs(filePath);
                ///加水印
                this.AddWatermark(filePath, this.watermarkTextBox.Text);
                image.ImageUrl = string.Format("~/{0}", FileUpload1.PostedFile.FileName);
            }
        }
    }

    /// <summary>
    /// 添加水印
    /// </summary>
    /// <param name="filePath"></param>
    /// <param name="watermaterText"></param>
    private void AddWatermark(string filePath, string watermaterText)
    {
        using (TextWatermarkPainter painter = new TextWatermarkPainter(filePath, 80, watermaterText))
        {
            painter.FontColor = System.Drawing.Color.DarkGreen;
            painter.PaintWaterMark();
        }

    }
}