AJAX實(shí)現(xiàn)圖片預(yù)覽與上傳及生成縮略圖的方法

//ajax保存數(shù)據(jù)，后臺(tái)方法里實(shí)現(xiàn)此方法 
function SaveData() {　 
    filename = document.getElementById("idFile").value; 
    result =test_test_aspx.SaveData(filename).value; 
    if (result) { 
      alert("保存成功！");      
    } 
    return false; 
  }  
//實(shí)現(xiàn)預(yù)覽功能 
  function DrawImage(ImgD) { 
    var preW = 118; 
    var preH = 118; 
    var image = new Image(); 
    image.src = ImgD.src; 
    if (image.width > 0  image.height > 0) { 
      flag = true; 
      if (image.width / image.height >= preW/ preH) { 
        if (image.width > preW) { 
          ImgD.width = preW; 
          ImgD.height = (image.height * preW) / image.width; 
        } 
        else { 
          ImgD.width = image.width; 
          ImgD.height = image.height; 
        } 
        ImgD.alt = image.width + "x" + image.height; 
      } 
      else { 
        if (image.height > preH) { 
          ImgD.height = preH; 
          ImgD.width = (image.width * preH) / image.height; 
        } 
        else { 
          ImgD.width = image.width; 
          ImgD.height = image.height; 
        } 
        ImgD.alt = image.width + "x" + image.height; 
      } 
    } 
  } 
//當(dāng)idFile內(nèi)容改變時(shí) 
  function FileChange(Value) { 
    flag = false; 
    document.getElementById("showImg").style.display = "none";    
    document.getElementById("idImg").width = 10; 
    document.getElementById("idImg").height = 10; 
    document.getElementById("idImg").alt = ""; 
    document.getElementById("idImg").src = Value; 
  } 

div class="cbs"> 
div class="l">label>圖片:/label>/div> 
div> 
  input id="idFile" name="pic" type="file" runat="server" onchange="FileChange(this.value);" /> 
/div> 
    /div>  
    div class="cbs"> 
div class="l">label>預(yù)覽:/label>/div> 
div> 
  img id="idImg" height="0" width="0" src="" alt="" onload="DrawImage(this);" /> //實(shí)現(xiàn)預(yù)覽 
  img id="showImg" width="118" height="118" alt="" runat="server" style="display:none"/>  //加這個(gè)主要是為了實(shí)現(xiàn)查看時(shí)顯示圖片，因?yàn)樯厦娴模╥dImg）加上runat="server"　報(bào)錯(cuò)，如有好的方法可以留言     
/div> 
/div>    

[Ajax.AjaxMethod()] 
public bool SaveData(string fileNamePath) 
{ 
  string serverFileName = ""; 
  string sThumbFile = "";   
  string sSavePath = "~/Files/"; 
  int intThumbWidth = 118; 
  int intThumbHeight = 118; 
  string sThumbExtension = "thumb_"; 
  try 
  { 
 //獲取要保存的文件信息 
 FileInfo file = new FileInfo(fileNamePath); 
 //獲得文件擴(kuò)展名 
 string fileNameExt = file.Extension; 
 
 //驗(yàn)證合法的文件 
 if (CheckFileExt(fileNameExt)) 
 { 
   //生成將要保存的隨機(jī)文件名 
   string fileName = GetFileName() + fileNameExt; 
   //檢查保存的路徑 是否有/結(jié)尾 
   if (sSavePath.EndsWith("/") == false) sSavePath = sSavePath + "/"; 
 
   //按日期歸類保存 
   string datePath = DateTime.Now.ToString("yyyyMM") + "/" + DateTime.Now.ToString("dd") + "/"; 
   if (true) 
   { 
 sSavePath += datePath; 
   } 
   //獲得要保存的文件路徑 
   serverFileName = sSavePath + fileName; 
   //物理完整路徑 
   string toFileFullPath = HttpContext.Current.Server.MapPath(sSavePath); 
 
   //檢查是否有該路徑 沒有就創(chuàng)建 
   if (!Directory.Exists(toFileFullPath)) 
   { 
 Directory.CreateDirectory(toFileFullPath); 
   } 
 
   //將要保存的完整文件名  
   string toFile = toFileFullPath + fileName; 
 
   ///創(chuàng)建WebClient實(shí)例 
   WebClient myWebClient = new WebClient(); 
   //設(shè)定windows網(wǎng)絡(luò)安全認(rèn)證  
   myWebClient.Credentials = CredentialCache.DefaultCredentials; 
   
   //要上傳的文件 
   FileStream fs = new FileStream(fileNamePath, FileMode.Open, FileAccess.Read); 
   //FileStream fs = OpenFile(); 
   BinaryReader r = new BinaryReader(fs); 
   //使用UploadFile方法可以用下面的格式 
   //myWebClient.UploadFile(toFile, "PUT",fileNamePath); 
   byte[] postArray = r.ReadBytes((int)fs.Length); 
   Stream postStream = myWebClient.OpenWrite(toFile, "PUT"); 
   if (postStream.CanWrite) 
   { 
 postStream.Write(postArray, 0, postArray.Length); 
   } 
   postStream.Close(); 
   //以上為原圖 
   try 
   { 
 //原圖加載  
  using (System.Drawing.Image sourceImage = System.Drawing.Image.FromFile(System.Web.HttpContext.Current.Server.MapPath(serverFileName))) 
 { 
   //原圖寬度和高度  
   int width = sourceImage.Width; 
   int height = sourceImage.Height; 
   int smallWidth; 
   int smallHeight; 
 
   //獲取第一張繪制圖的大小,(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(dāng)前文件夾下是否同名稱文件存在  
  int file_append = 0; 
   sThumbFile = sThumbExtension + System.IO.Path.GetFileNameWithoutExtension(fileName) + fileNameExt; 
 
   while (System.IO.File.Exists(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sThumbFile))) 
   { 
  file_append++; 
  sThumbFile = sThumbExtension + System.IO.Path.GetFileNameWithoutExtension(fileName) + 
file_append.ToString() + fileNameExt; 
   } 
   //縮略圖保存的絕對(duì)路徑  
   string smallImagePath = System.Web.HttpContext.Current.Server.MapPath(sSavePath) + sThumbFile; 
 
   //新建一個(gè)圖板,以最小等比例壓縮大小繪制原圖  
   using (System.Drawing.Image bitmap = new System.Drawing.Bitmap(smallWidth, smallHeight)) 
   { 
  //繪制中間圖  
  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(gè)圖板,以縮略圖大小繪制中間圖  
  using (System.Drawing.Image bitmap1 = new System.Drawing.Bitmap(intThumbWidth, intThumbHeight)) 
  { 
//繪制縮略圖  
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); 
   return true; 
   } 
  } 
   } 
 } 
   } 
   catch 
   { 
 //出錯(cuò)則刪除  
 System.IO.File.Delete(System.Web.HttpContext.Current.Server.MapPath(serverFileName)); 
 return false; 
   } 

 } 
 else 
 { 
   return false; 
 } 
  } 
  catch (Exception e) 
  { 
 return false; 
  } 
} 
/// summary> 
/// 檢查是否為合法的上傳文件 
/// /summary> 
/// param name="_fileExt">/param> 
/// returns>/returns> 
private bool CheckFileExt(string _fileExt) 
{ 
  string[] allowExt = new string[] { ".gif", ".jpg", ".jpeg" }; 
  for (int i = 0; i  allowExt.Length; i++) 
  { 
 if (allowExt[i] == _fileExt) { return true; } 
  } 
  return false; 
 
} 
   //生成隨機(jī)數(shù)文件名 
public static string GetFileName() 
{ 
  Random rd = new Random(); 
  StringBuilder serial = new StringBuilder(); 
  serial.Append(DateTime.Now.ToString("yyyyMMddHHmmssff")); 
  serial.Append(rd.Next(0, 999999).ToString()); 
  return serial.ToString(); 
 
}