用ASP.NET 处理图象:从数据库中读取图象,并在图象上加上版权信息

来源：互联网发布：如何更换淘宝店铺头像编辑：程序博客网时间：2024/04/30 05:40

我是一个ASP.NET的新手，出于对程序的热爱而自学程序设计，作为一非计算机专业人氏（我是一个小会计）常常感到学习的困难，希望得到各位大侠的帮助，以提高自己的水平，以下是我学习过程中写的一个关于数据库图象字段处理的程序，也可以说是学习笔记吧，希望得到各位的指正。

程序设计思路:

1:用ADO.NET从一个BLOB字段中读取一幅图象,方法:在图象列上执行一个SELECT语句,并使用EXCUTESCALAR方法取得结果,然后将它保存在字节数组中;

2:将图象数组写入memory strean 中,并将流读入一个Image对象中;

3:用GDI+类对图形进行处理,将版权信息写到图象相应的位置

using System;

using System.Data;

using System.Configuration;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Web.UI.HtmlControls;

using System.Data.SqlClient;

using System.Drawing;

using System.Drawing.Imaging;

using System.IO;

using System.Runtime.Serialization.Formatters.Binary;

///<summary>

///实现从SQLSERVER数据库中读取图象数据，并为图象加上版权标记，

///实现IHTTPHANDLER接口

///</summary>

public class imagehandle:IHttpHandler

{

public imagehandle()

{

}

#region IHttpHandler 成员

public bool IsReusable

{

get { return true; }

}

public void ProcessRequest(HttpContext context)

{

int id = 1;

bool result = Int32.TryParse(context.Request.QueryString["id"], out id);

string cnnstr = "Data Source=CW31;Initial Catalog=Northwind;Integrated Security=True";

string cmdstr = "select photo from employees where employeeid=" + id;

SqlConnection cnn = new SqlConnection(cnnstr);

SqlCommand cmn = new SqlCommand(cmdstr, cnn);

byte[] image = null;

try

{

cnn.Open();

image = (byte[])cmn.ExecuteScalar();

}

catch (Exception E)

{

throw new Exception(E.Message);

}

finally

{

cnn.Close();

}

if (image != null)

{

System.Drawing.Image limage = ReadImage(image);

Bitmap bmp = new Bitmap(limage);

Graphics g = Graphics.FromImage(bmp);

StringFormat strfmt = new StringFormat();

strfmt.Alignment = StringAlignment.Center;

SolidBrush btmforcolor = new SolidBrush(Color.White);

SolidBrush btmbaclcolor = new SolidBrush(Color.Black);

//固定版权写入图形的位置

SizeF textf = new SizeF();

string mycopright = context.Request.UserHostName;

Font f = new Font("黑体", 12, FontStyle.Italic);

textf = g.MeasureString(mycopright, f);

int bheight = bmp.Height;

int bweght = bmp.Width;

float theight = textf.Height;

float tweight = textf.Width;

float x = ((float)bweght - tweight - 3);

float y = ((float)bheight-theight - 3);

float w = ((float)x + tweight);

float h = ((float)y + theight);

RectangleF textarea = new RectangleF(x, y, w, h);

g.FillRectangle(btmbaclcolor,textarea);

g.DrawString(mycopright, f, btmforcolor, textarea);

btmforcolor.Dispose();

btmbaclcolor.Dispose();

f.Dispose();

g.Dispose();

//将图象保存到输出流中

bmp.Save(context.Response.OutputStream, ImageFormat.Jpeg);

}

//将图象字节写并成像的处理程序,将字节数组转为流,并将流形成图象

public System.Drawing.Image ReadImage(byte[] bytes)

{

MemoryStream ms = new MemoryStream(bytes,78,bytes.Length-78);

return System.Drawing.Image.FromStream(ms);

ms.Close();

}

#endregion

}

在cofig文件中注册 imagehandle

3、使用图象处理程序例子

<%@ 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>
        <span style="color: #66ccff"><span style="font-size: 36pt">Employees photo<br />
        </span>
            <table>
                <tr>
                    <td style="width: 100px">

        <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" DataSourceID="SqlDataSource1"
            DataTextField="LastName" DataValueField="EmployeeID" Width="150px">
        </asp:DropDownList></td>
                    <td style="width: 100px">
                    </td>
                    <td style="width: 100px">
                    </td>
                </tr>
                <tr>
                    <td style="width: 100px">
                        <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:NorthwindConnectionString %>"
            SelectCommand="SELECT [EmployeeID], [LastName] FROM [Employees]"></asp:SqlDataSource>
                    </td>
                    <td style="width: 100px">
                    </td>
                    <td style="width: 100px">
                    </td>
                </tr>
                <tr>
                    <td colspan="3">
        <asp:Image ID="Image1" runat="server" Height="286px" Width="409px"/></td>
                </tr>
            </table>
        <br />
        </span>
        <br />
         
        <br />
    </div>
    </form>
</body>
</html>

//DropDownList控件的selectitemvalue属性与IMAGE的imagurl属性相关，其程序实现如下：

protected void Page_PreRender(object sender, EventArgs e)
    {
        string url;
        if (!IsPostBack)
        {
            url = "dbimage.axd?id=1";
        }
        else
        {
            url = string.Format("dbimage.axd?id={0}", DropDownList1.SelectedValue);
        }
        Image1.ImageUrl = url;
    }

例程实现效果

Employees photo