使用ASP.NET内置类生成图片缩略图及水印_[Asp.Net教程]
ASP.NET Image Generation内置了ImageResizeTransform类，可以实现图片大小调整功能。也可以扩展ImageTransform实现自己的图片变换类。
下面使用ASP.NET Image Generation生成图片缩略图及水印的代码。

数据库:

CREATE TABLE t_images
(
image_id INT,
image_data IMAGE,
last_modified_date, DATETIME
)


Default.aspx:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="NET35Lab.GeneratedImage.Web._Default" %>

<%@ Register Assembly="Microsoft.Web.GeneratedImage" Namespace="Microsoft.Web" TagPrefix="cc1" %>









RepeatDirection="Horizontal" CellPadding="4" CellSpacing="4">

Timestamp=’<%# Eval("last_modified_date") %>’>

’ />








ProviderName="System.Data.SqlClient" SelectCommand="SELECT [image_id], [image_data], [last_modified_date] FROM [t_images]">






ImageHandler1.ashx:

<%@ WebHandler Language="C#" CodeBehind="ImageHandler1.ashx.cs" Class="NET35Lab.GeneratedImage.Web.ImageHandler1" %>


ImageHandler1.ashx.cs :

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Microsoft.Web;
using System.Collections.Specialized;
using System.Data.SqlClient;
using System.Drawing;

namespace NET35Lab.GeneratedImage.Web
{

public class ImageHandler1 : ImageHandler
{

public ImageHandler1()
{
this.ImageTransforms.Add(new ImageResizeTransform { Width = 320, Mode = ImageResizeMode.Fit });
this.ImageTransforms.Add(new CopyrightTransform { Text = "Guushuuse .NET" });
this.EnableClientCache = true;
this.EnableServerCache = true;

}

public override ImageInfo GenerateImage(NameValueCollection parameters)
{

int imageID = int.Parse(parameters["imageid"]);

SqlConnection connection = new SqlConnection(
@"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database.mdf;Integrated Security=True;User Instance=True;");

connection.Open();

SqlCommand command = new SqlCommand("select image_data from t_images where image_id=" + imageID, connection);

SqlDataReader dr = command.ExecuteReader();

dr.Read();

return new ImageInfo((Byte[])dr[0]);

}
}

public class CopyrightTransform : ImageTransform
{
private const int VERTICAL_PADDING = 5;
private const int HORIZONAL_PADDING = 5;

public string Text { get; set; }
public Font Font { get; set; }
public Color FontColor { get; set; }

public CopyrightTransform()
{
//Assign Defaults
FontColor = Color.FromArgb(128, 255, 0, 0);
Font = new Font("Courier", 13);
}


public override System.Drawing.Image ProcessImage(System.Drawing.Image img)
{
Graphics gra = Graphics.FromImage(img);
SizeF sz = gra.MeasureString(Text, Font);
gra.DrawString(Text, Font, new SolidBrush(FontColor), img.Width - sz.Width - HORIZONAL_PADDING, img.Height - sz.Height - VERTICAL_PADDING);
return img;
}

public override string UniqueString
{
get
{
return base.UniqueString + Text + FontColor.ToString() + Font.ToString();
}
}
}
}


运行效果: