/// <summary>
 /// 為圖片生成縮略圖  
 /// </summary>
 /// <param name="phyPath">原圖片的路徑</param>
/// <param name="width">縮略圖寬</param>
 /// <param name="height">縮略圖高</param>
 /// <returns></returns>
public System.Drawing.Image GetThumbnail(System.Drawing.Image image, int width, intheight)
{
Bitmap bmp = newBitmap(width, height);
//從Bitmap創建一個System.Drawing.Graphics
System.Drawing.Graphics gr = System.Drawing.Graphics.FromImage(bmp);
//設置 
gr.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
//下面這個也設成高質量
gr.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
//下面這個設成High
gr.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
//把原始圖像繪制成上面所設置寬高的縮小圖
System.Drawing.Rectangle rectDestination = newSystem.Drawing.Rectangle(0, 0, width, height);
gr.DrawImage(image, rectDestination, 0, 0, image.Width, image.Height, GraphicsUnit.Pixel);
returnbmp;
}
 

HttpPostedFile file = photoFile.PostedFile;
if(!file.ContentType.Contains("image"))
{
return"照片格式不合法";
}
stringext = Path.GetExtension(file.FileName).ToLower();
if (ext != ".jpg" && ext != ".gif" && ext != ".png"&& ext != ".jpeg")
{
return"請您上傳jpg、gif、png圖片";
}
if(file.ContentLength > 5 * 1024 * 1024)
{
return"請您上傳512字節內的圖片";
}
stringnewName = Guid.NewGuid().ToString();
stringtempPath = "upload/";
stringimg = tempPath + newName + ext;
stringfilePath = Server.MapPath(img);
if(!Directory.Exists(tempPath))
{
Directory.CreateDirectory(tempPath);
}
using(System.Drawing.Image originalImage = System.Drawing.Image.FromStream(file.InputStream))
{
GetThumbnail(originalImage, 504, 374).Save(filePath);

public void  MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height)
{
//獲取原始圖片 
System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);
//縮略圖畫布寬高 
int towidth = width;
int toheight = height;
//原始圖片寫入畫布坐標和寬高(用來設置裁減溢出部分) 
int x = 0;
int y = 0;
int ow = originalImage.Width;
int oh = originalImage.Height;
//原始圖片畫布,設置寫入縮略圖畫布坐標和寬高(用來原始圖片整體寬高縮放) 
int bg_x = 0;
int bg_y = 0;
int bg_w = towidth;
int bg_h = toheight;
//倍數變量 
double multiple = 0;
//獲取寬長的或是高長與縮略圖的倍數 
if (originalImage.Width >= originalImage.Height)
multiple = (double)originalImage.Width / (double)width;
else
multiple = (double)originalImage.Height / (double)height;
//上傳的圖片的寬和高小等于縮略圖 
if (ow <= width && oh <= height)
{
//縮略圖按原始寬高 
bg_w = originalImage.Width;
bg_h = originalImage.Height;
//空白部分用背景色填充 
bg_x = Convert.ToInt32(((double)towidth - (double)ow) / 2);
bg_y = Convert.ToInt32(((double)toheight - (double)oh) / 2);
}
//上傳的圖片的寬和高大于縮略圖 
else
{
//寬高按比例縮放 
bg_w = Convert.ToInt32((double)originalImage.Width / multiple);
bg_h = Convert.ToInt32((double)originalImage.Height / multiple);
//空白部分用背景色填充 
bg_y = Convert.ToInt32(((double)height - (double)bg_h) / 2);
bg_x = Convert.ToInt32(((double)width - (double)bg_w) / 2);
}
//新建一個bmp圖片,并設置縮略圖大小. 
System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
//新建一個畫板 
System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);
//設置高質量插值法 
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBilinear;
//設置高質量,低速度呈現平滑程度 
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
//清空畫布并設置背景色 
g.Clear(System.Drawing.ColorTranslator.FromHtml("#F2F2F2"));
//在指定位置并且按指定大小繪制原圖片的指定部分 
//第一個System.Drawing.Rectangle是原圖片的畫布坐標和寬高,第二個是原圖片寫在畫布上的坐標和寬高,最后一個參數是指定數值單位為像素 
g.DrawImage(originalImage, new System.Drawing.Rectangle(bg_x, bg_y, bg_w, bg_h), new System.Drawing.Rectangle(x, y, ow, oh), System.Drawing.GraphicsUnit.Pixel);
try
{
//獲取圖片類型 
string fileExtension = System.IO.Path.GetExtension(originalImagePath).ToLower();
//按原圖片類型保存縮略圖片,不按原格式圖片會出現模糊,鋸齒等問題. 
switch (fileExtension)
{
case ".gif": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Gif); break;
case ".jpg": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg); break;
case ".bmp": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Bmp); break;
case ".png": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Png); break;
}
}
catch (System.Exception e)
{
throw e;
}
finally
{
originalImage.Dispose();
bitmap.Dispose();
g.Dispose();
}
}