.Net 下获得清晰的缩略图

来源：互联网发布：怎么用mac下载炉石编辑：程序博客网时间：2024/04/29 20:56

最近碰到这样一个需求：把图片保存到数据库中，然后作为上传人的头像之类的。本着程序员的优良“惰性”Google了一把，找到了一大把一大把代码，试了很多号称能得到清晰缩略图的，结果就不用说了。最终在一开源项目中找到了解决办法，为了让后来人免受我所受过的煎熬，所以放出代码！

写一个上传页面：

<%@ Page language="c#" Codebehind="UploadPictureConvertTo.aspx.cs" AutoEventWireup="false" Inherits="PicturesToDB.UI.UploadPictureConvertTo" %>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >

<HTML>

<HEAD>

<title>UploadPicture</title>

function ShowImage(value,img)

{

//alert(value);该脚本来源于网络

//检测盘符

//alert(value.indexOf(':'));

//检测文件是否有扩展名

//alert(value.length-value.lastIndexOf('.'));

//取文件扩展名

//alert(value.substr(value.length-3,3));

//检测文件扩展名是否合法

//alert(CheckExt(value.substr(value.length-3,3)));

if(value.length>5&&value.indexOf(':')==1&&(value.length-value.lastIndexOf('.'))==4&&CheckExt(value.substr(value.length-3,3)))

{

img.src=value;

img.alt="本地图片预览";

img.style.visibility="visible";

}

else

{

img.style.visibility="hidden";

}

//检查扩展名是否合法,合法返回True

function CheckExt(ext)

{

//这里设置允许的扩展名

var AllowExt="jpg|gif|jpeg|png|bmp";

var ExtOK=false;

var ArrayExt;

if(AllowExt.indexOf('|')!=-1)

{

ArrayExt=AllowExt.split('|');

for(i=0;i<ArrayExt.length;i++)

{

if(ext.toLowerCase()==ArrayExt[i])

{

ExtOK=true;

break;

}

else

{

ArrayExt=AllowExt;

if(ext.toLowerCase()==ArrayExt)

{

ExtOK=true;

}

return ExtOK;

}

</script>

</HEAD>

<table>

<tr>

</tr>

<tr>

<td>请选择上传图片</td>

<td><input id="PictureFile" name="PictureFile" type="file" onchange="javascript:ShowImage(this.value,document.getElementById('img'))"

runat="server"></td>

</tr>

<tr>

<td>

<asp:TextBox id="TextBox1" runat="server"></asp:TextBox></td>

</tr>

<tr>

<asp:Button id="Button1" runat="server" Text="提交"></asp:Button></td>

</tr>

</table>

</form>

</body>

</HTML>

上传按钮的Click事件，以及生成缩略图的方法

private void Button1_Click(object sender, System.EventArgs e)

{

//没有做文件类型检测，自己加上可以参考清清月儿的Blog

//http://blog.csdn.net/21aspnet/archive/2007/04/01/1548696.aspx

HttpPostedFile picture = PictureFile.PostedFile;

PictureLength = picture.ContentLength;

try

{

if (PictureLength == 0)

{

Response.Write("<script language=javascript>alert('请选择上传文件');</script>");

}

else

{

Stream PictureStram =picture.InputStream;

MemoryStream ReduceStream=new MemoryStream();

ReduceStream=ResizeImageFile(PictureStram);

Byte[] PictureByte =ReduceStream.ToArray();

string strConn = @"Data Source=localhost;Initial Catalog=CommonCompontTest;User ID=sa;Pwd=sa";

SqlConnection sqlConn = new SqlConnection(strConn);

string sqlCommand = @"INSERT INTO [PicturnsTable]( [PictureBinary], [PictureType], [PictureDes], [PiacureSize])

VALUES( @PictureBinary ,@PictureDes,@PiacureSize)";

SqlCommand sqlCMD = new SqlCommand(sqlCommand, sqlConn);

sqlCMD.Parameters.Add("@PictureBinary", SqlDbType.Binary).Value = PictureByte;

sqlCMD.Parameters.Add("@PictureDes", SqlDbType.VarChar, 200).Value = TextBox1.Text.Trim();

sqlCMD.Parameters.Add("@PiacureSize", SqlDbType.Int).Value = PictureByte.Length;

sqlConn.Open();

sqlCMD.ExecuteNonQuery();

sqlConn.Close();

Response.Write(@"<script language=javascript>alert('文件上传功');window.location.href='UploadPictureConvertTo.aspx';</script>");

//Response.Redirect("UploadPicture.aspx");

}

catch (Exception ex)

{

Console.Write(ex.Message);

}

//生成缩略图的代码

private static MemoryStream ResizeImageFile(Stream stream)

{

Size newSize=new Size(320,240);

using (System.Drawing.Image oldImage = System.Drawing.Image.FromStream(stream))

{

using (Bitmap newImage = new Bitmap(newSize.Width, newSize.Height, PixelFormat.Format24bppRgb))

{

using (Graphics canvas = Graphics.FromImage(newImage))

{

canvas.SmoothingMode = SmoothingMode.AntiAlias;

canvas.InterpolationMode = InterpolationMode.HighQualityBicubic;

canvas.PixelOffsetMode = PixelOffsetMode.HighQuality;

canvas.DrawImage(oldImage, new Rectangle(new Point(0, 0), newSize));

MemoryStream m = new MemoryStream();

newImage.Save(m, ImageFormat.Jpeg);

return m;

}

数据库表结构很简单，这里就不说了

然后就是获取图片的页面，写得很简单，将就着看哈

private void Page_Load(object sender, System.EventArgs e)

{

// 在此处放置用户代码以初始化页面

int PictureID = Convert.ToInt32(Request.Params["PictureID"]); //ImgID为图片ID

//建立数据库链接

string strConn = @"Data Source=localhost;Initial Catalog=CommonCompontTest;User ID=sa;Pwd=sa";

SqlConnection sqlConn = new SqlConnection(strConn);

String SqlCmd = "SELECT [PictureID], [PictureBinary], PictureDes], [PiacureSize] FROM .[PicturnsTable] where PictureID=@PictureID";

SqlCommand SQLCmd = new SqlCommand(SqlCmd, sqlConn);

SQLCmd.Parameters.Add("@PictureID",SqlDbType.Int).Value=PictureID;

sqlConn.Open();

SqlDataReader SqlReader = SQLCmd.ExecuteReader();

SqlReader.Read();

//输出图象文件二进制数制

Response.OutputStream.Write((byte[])SqlReader["PictureBinary"], 0, (int)SqlReader["PiacureSize"]);

Response.End();

sqlConn.Close();

//很简单吧^_^

}

查看图片的页面就用个Gridview就可以了，更简单的就是，这样写在VS IDE中直接就可以看到了，麻烦就是每次都要改^_^

<%@ Page language="c#" Codebehind="ShowPicture.aspx.cs" AutoEventWireup="false" Inherits="PicturesToDB.UI.ShowPicture" %>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >

<HTML>

<HEAD>

<title>ShowPicture</title>

</HEAD>

</form>

</body>

</HTML>

代码就这样，希望能被需要的人Google到呵呵