在上一篇文章中讲到了关于C#上传图片添加文字水印的方法，这个章节中则是添加半透明的图片水印的方法。请参：http://hi.baidu.com/1987raymond/blog/item/017a6a4ee9a8ca01b2de0543.html
下面是ImageWatermarkPainter类的实现：
/* ***********************************************
* Author: 1987raymond
* Team: Juice Sharing
* Created Time: 2009-3-11 20:53:14
* CopyRight: Juice Sharing 团队版权所有 保留一切权利
* NameSpace: Juice.Common.Drawing
* Class/Interface: ImageWatermarkPainter
* ***********************************************/
using System;
using System.Text;
using System.IO;
using System.Drawing;
using System.Drawing.Imaging;
namespace Juice.Common.Drawing
{
/// <summary>
/// 图片水印绘制器
/// </summary>
public sealed class ImageWatermarkPainter : WatermarkPainter
{
/// <summary>
/// 构造函数
/// </summary>
/// <param name="rawImagePath"></param>
/// <param name="alpha"></param>
/// <param name="watermarkImage"></param>
public ImageWatermarkPainter(string rawImagePath, int alpha, string watermarkImage)
: base(rawImagePath, alpha)
{
WatermarkImagePath = watermarkImage;
}
private string m_WatermarkImagePath;
/// <summary>
/// 水印图片路径
/// </summary>
public string WatermarkImagePath
{
get { return m_WatermarkImagePath; }
set { m_WatermarkImagePath = value; }
}
private Image m_WatermarkImage;
/// <summary>
/// 水印图片对象
/// </summary>
public Image WatermarkImage
{
get
{
if (null == m_WatermarkImage)
m_WatermarkImage = Image.FromFile(WatermarkImagePath);
return m_WatermarkImage;
}
}
/// <summary>
/// 添加水印
/// </summary>
/// <param name="graphics"></param>
/// <param name="newImage"></param>
/// <returns></returns>
protected override bool AddWatermark(Graphics graphics, Bitmap newImage)
{
if (string.IsNullOrEmpty(WatermarkImagePath))
return false;
if (!File.Exists(WatermarkImagePath))
throw new FileNotFoundException(string.Format("file {0} not found.", WatermarkImagePath));
if ((WatermarkImage.Width + 10) > newImage.Width || (WatermarkImage.Height + 10) > newImage.Height)
return false;
using (ImageAttributes attributes = new ImageAttributes())
{
float alpha = WatermarkAlpha / 255.0f;
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, alpha, 0.0f},
new float[] {0.0f, 0.0f, 0.0f, 0.0f, 1.0f}
};
ColorMatrix colorMatrix = new ColorMatrix(colorMatrixElements);
///设置颜色调整矩阵
attributes.SetColorMatrix(colorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
///水印图片的位置，默认为右下角
int x = newImage.Width - WatermarkImage.Width - 10;
int y = newImage.Height - WatermarkImage.Height - 10;
///开始绘制水印
graphics.DrawImage(WatermarkImage, new Rectangle(x, y, WatermarkImage.Width, WatermarkImage.Height), 0, 0, WatermarkImage.Width, WatermarkImage.Height, GraphicsUnit.Pixel, attributes);
}
return true;
}
public override void Dispose()
{
if (null != WatermarkImage)
WatermarkImage.Dispose();
base.Dispose();
}
}
}
下面查看使用的方法：
default.aspx的内容如下：
<%@ 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" />
<asp:Button ID="uploadAndAddImageBtn" runat="server" Text="上传图片并且添加半透明的图片水印"
onclick="uploadAndAddImageBtn_Click" />
<br />加了水印的图像如下：
<asp:Image ID="image" runat="server" />
</div>
</form>
</body>
</html>
default.aspx.cs的内容如下：
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}", Server.HtmlEncode(FileUpload1.PostedFile.FileName)));
///保存文件
FileUpload1.SaveAs(filePath);
///加水印
this.AddWatermark(filePath, this.watermarkTextBox.Text);
image.ImageUrl = string.Format("~/{0}", Server.HtmlEncode(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();
}
}
protected void uploadAndAddImageBtn_Click(object sender, EventArgs e)
{
if (FileUpload1.HasFile)
{
string contentType = FileUpload1.PostedFile.ContentType;
if (contentType.StartsWith("image/"))
{
string filePath = Server.MapPath(string.Format("~/{0}", Server.HtmlEncode(FileUpload1.PostedFile.FileName)));
///保存文件
FileUpload1.SaveAs(filePath);
///加水印
this.AddImageWatermark(filePath);
image.ImageUrl = string.Format("~/{0}", Server.HtmlEncode(FileUpload1.PostedFile.FileName));
}
}
}
/// <summary>
/// 添加图片水印
/// </summary>
/// <param name="filePath"></param>
private void AddImageWatermark(string filePath)
{
using (WatermarkPainter painter = new ImageWatermarkPainter(filePath, 180, Server.MapPath("~/watermark.gif")))
{
painter.PaintWaterMark();
}
}
}
其显示效果如下：
点击“上传图片并且添加半透明的图片水印”按钮后效果如下：
上图中右下角的绿色的标志则是水印，需要说明的是：
WatermarkPainter painter = new ImageWatermarkPainter(filePath, 180, Server.MapPath("~/watermark.gif"))) 这个地方就是创建水印绘制器的实例，且为图片水印绘制器，透明度为180（介于0-255之间），水印图片的地址是~/watermark.gif
好了关于上传图片添加水印的方法就这些了，大家可以修改使得类更加的灵活和完善，如果以上有错误也请大家指教
