首先要引入命名空間：using System.IO;
using System.Web.UI.HtmlControls;
using System.Drawing;
/// <summary>
/// asp.net上傳圖片並生成縮略圖
/// </summary>
/// <param name="upImage">HtmlInputFile控件</param>
/// <param name="sSavePath">保存的路徑,些爲相對服務器路徑的下的文件夾</param>
/// <param name="sThumbExtension">縮略圖的thumb</param>
/// <param name="intThumbWidth">生成縮略圖的寬度</param>
/// <param name="intThumbHeight">生成縮略圖的高度</param>
/// <returns>縮略圖名稱</returns>
public string UpLoadImage(HtmlInputFile upImage, string sSavePath, string sThumbExtension, int intThumbWidth, int intThumbHeight)
{
string sThumbFile = "";
string sFilename = "";
if (upImage.PostedFile != null)
{
HttpPostedFile myFile = upImage.PostedFile;
int nFileLen = myFile.ContentLength;
if (nFileLen == 0)
return "沒有選擇上傳圖片";
//獲取upImage選擇文件的擴展名
string extendName = System.IO.Path.GetExtension(myFile.FileName).ToLower();
//判斷是否爲圖片格式
if (extendName != ".jpg" && extendName != ".jpg" && extendName != ".gif" && extendName != ".bmp" && extendName != ".png")
return "圖片格式不正確";
byte[] myData = new Byte[nFileLen];
myFile.InputStream.Read(myData, 0, nFileLen);
sFilename = System.IO.Path.GetFileName(myFile.FileName);
int file_append = 0;
//檢查當前文件夾下是否有同名圖片,有則在文件名+1
while (System.IO.File.Exists(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename)))
{
file_append++;
sFilename = System.IO.Path.GetFileNameWithoutExtension(myFile.FileName)
+ file_append.ToString() + extendName;
}
System.IO.FileStream newFile
= new System.IO.FileStream(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename),
System.IO.FileMode.Create, System.IO.FileAccess.Write);
newFile.Write(myData, 0, myData.Length);
newFile.Close();
//以上爲上傳原圖
try
{
//原圖加載
using (System.Drawing.Image sourceImage = System.Drawing.Image.FromFile(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename)))
{
//原圖寬度和高度
int width = sourceImage.Width;
int height = sourceImage.Height;
int smallWidth;
int smallHeight;
//獲取第一張繪製圖的大小,(比較 原圖的寬/縮略圖的寬 和 原圖的高/縮略圖的高)
if (((decimal)width) / height <= ((decimal)intThumbWidth) / intThumbHeight)
{
smallWidth = intThumbWidth;
smallHeight = intThumbWidth * height / width;
}
else
{
smallWidth = intThumbHeight * width / height;
smallHeight = intThumbHeight;
}
//判斷縮略圖在當前文件夾下是否同名稱文件存在
file_append = 0;
sThumbFile = sThumbExtension + System.IO.Path.GetFileNameWithoutExtension(myFile.FileName) + extendName;
while (System.IO.File.Exists(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sThumbFile)))
{
file_append++;
sThumbFile = sThumbExtension + System.IO.Path.GetFileNameWithoutExtension(myFile.FileName) +
file_append.ToString() + extendName;
}
//縮略圖保存的絕對路徑
string smallImagePath = System.Web.HttpContext.Current.Server.MapPath(sSavePath) + sThumbFile;
//新建一個圖板,以最小等比例壓縮大小繪製原圖
using (System.Drawing.Image bitmap = new System.Drawing.Bitmap(smallWidth, smallHeight))
{
//繪製中間圖
using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap))
{
//高清,平滑
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
g.Clear(Color.Black);
g.DrawImage(
sourceImage,
new System.Drawing.Rectangle(0, 0, smallWidth, smallHeight),
new System.Drawing.Rectangle(0, 0, width, height),
System.Drawing.GraphicsUnit.Pixel
);
}
//新建一個圖板,以縮略圖大小繪製中間圖
using (System.Drawing.Image bitmap1 = new System.Drawing.Bitmap(intThumbWidth, intThumbHeight))
{
//繪製縮略圖
using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap1))
{
//高清,平滑
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
g.Clear(Color.Black);
int lwidth = (smallWidth - intThumbWidth) / 2;
int bheight = (smallHeight - intThumbHeight) / 2;
g.DrawImage(bitmap, new Rectangle(0, 0, intThumbWidth, intThumbHeight), lwidth, bheight, intThumbWidth, intThumbHeight, GraphicsUnit.Pixel);
g.Dispose();
bitmap1.Save(smallImagePath, System.Drawing.Imaging.ImageFormat.Jpeg);
}
}
}
}
}
catch
{
//出錯則刪除
System.IO.File.Delete(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename));
return "圖片格式不正確";
}
//返回縮略圖名稱
return sThumbFile;
}
return "沒有選擇圖片";
}
這裏是頁面HTML代碼
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>無標題頁</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<input id="File1" runat="server" type="file" /></div><asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Button" />
</form>
</body>
</html>
最近是調用代碼
protected void Button1_Click(object sender, EventArgs e)
{
string a = this.UpLoadImage(this.File1, "UpLoad/", "thumb_", 118, 118);
}