asp.net上傳圖片產生縮圖

在asp.net中，上傳圖片功能或者是常用的，產生縮圖也是常用的。baidu或者google，c#的方法也是很多的，但是一用卻發現縮圖不清晰啊，縮圖片太大之類的事情，下面是我在處理圖片上的代碼，效果不錯，所以拿出來分享，(效果能達到一些繪圖軟體的效果)

代碼如下：

/// <summary>     /// asp.net上傳圖片並產生縮圖     /// </summary>     /// <param name="upImage">HtmlInputFile控制項</param>     /// <param name="sSavePath">儲存的路徑,些為相對伺服器路徑的下的檔案夾</param>     /// <param name="sThumbExtension">縮圖的thumb</param>     /// <param name="intThumbWidth">產生縮圖的寬度</param>     /// <param name="intThumbHeight">產生縮圖的高度</param>     /// <returns>縮圖名稱</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";                        //擷取upImage選擇檔案的副檔名             string extendName = System.IO.Path.GetExtension(myFile.FileName).ToLower();             //判斷是否為圖片格式             if (extendName != ".jpg" && extendName != ".jpge" && 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;             //檢查當前檔案夾下是否有同名圖片,有則在檔案名稱+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();            //以上為上傳原圖            try             {                 //原圖載入                 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;                    //擷取第一張繪製圖的大小,(比較 原圖的寬/縮圖的寬 和 原圖的高/縮圖的高)                     if (((decimal)width) / height <= ((decimal)intThumbWidth) / intThumbHeight)                     {                         smallWidth = intThumbWidth;                         smallHeight = intThumbWidth * height / width;                     }                     else                     {                         smallWidth = intThumbHeight * width / height;                         smallHeight = intThumbHeight;                     }                    //判斷縮圖在當前檔案夾下是否同名稱檔案存在                     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;                     }                     //縮圖儲存的絕對路徑                     string smallImagePath = System.Web.HttpContext.Current.Server.MapPath(sSavePath) + sThumbFile;                    //建立一個圖板,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                             );                         }                         //建立一個圖板,以縮圖大小繪製中間圖                         using (System.Drawing.Image bitmap1 = new System.Drawing.Bitmap(intThumbWidth, intThumbHeight))                         {                             //繪製縮圖                             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";             }             //返回縮圖名稱             return sThumbFile;         }         return "沒有選擇圖片";     }

HtmlInputFile控制項我想大家都應該知道的，就是input type=file....這個會在後面的一起學asp.net章節中講解