使用ASP.NET Image Generation生成图片缩略图及水印

　　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

以下为引用的内容：
CREATE TABLE t_images
(
image_id INT,
image_data IMAGE,
last_modified_date, DATETIME
)

　　Default.aspx

以下为引用的内容：
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="NET35Lab.GeneratedImage.Web._Default" %>

<%@ Register Assembly="Microsoft.Web.GeneratedImage" Namespace="Microsoft.Web" TagPrefix="cc1" %>
<!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></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:DataList ID="DataList1" runat="server" DataSourceID="SqlDataSource1" RepeatColumns="2"
            RepeatDirection="Horizontal" CellPadding="4" CellSpacing="4">
            <ItemTemplate>
                <cc1:GeneratedImage ID="GeneratedImage1" runat="server" ImageHandlerUrl="~/ImageHandler1.ashx"
                    Timestamp='<%# Eval("last_modified_date") %>'>
                    <Parameters>
                        <cc1:ImageParameter Name="imageid" Value='<%# Eval("image_id") %>' />
                    </Parameters>
                </cc1:GeneratedImage>
                <br />
            </ItemTemplate>
        </asp:DataList>
    </div>
    <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database.mdf;Integrated Security=True;User Instance=True;"
        ProviderName="System.Data.SqlClient" SelectCommand="SELECT [image_id], [image_data], [last_modified_date] FROM [t_images]">
    </asp:SqlDataSource>
    </form>
</body>
</html>

　　ImageHandler1.ashx

以下为引用的内容：
<%@ WebHandler Language="C#" CodeBehind="ImageHandler1.ashx.cs" Class="NET35Lab.GeneratedImage.Web.ImageHandler1" %>

　　ImageHandler1.ashx.cs

以下为引用的内容：
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

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