ASP.NET实现上传图片并生成缩略图的方法


            本文实例讲述了ASP.NET实现上传图片并生成缩略图的方法。分享给大家供大家参考，具体如下：





protected void bt_upload_Click(object sender, EventArgs e)

{

  //检查上传文件的格式是否有效 

  if (this.UploadFile.PostedFile.ContentType.ToLower().IndexOf("image") < 0)

  {

   Response.Write("上传图片格式无效！");

   return;

  }

  //生成原图 

  Byte[] oFileByte = new byte[this.UploadFile.PostedFile.ContentLength];

  System.IO.Stream oStream = this.UploadFile.PostedFile.InputStream;

  System.Drawing.Image oImage = System.Drawing.Image.FromStream(oStream);

  int oWidth = oImage.Width; //原图宽度 

  int oHeight = oImage.Height; //原图高度 

  int tWidth = 100; //设置缩略图初始宽度 

  int tHeight = 100; //设置缩略图初始高度 

  //按比例计算出缩略图的宽度和高度 

  if (oWidth >= oHeight)

  {

   tHeight = (int)Math.Floor(Convert.ToDouble(oHeight) * (Convert.ToDouble(tWidth) / Convert.ToDouble(oWidth)));

  }

  else

  {

   tWidth = (int)Math.Floor(Convert.ToDouble(oWidth) * (Convert.ToDouble(tHeight) / Convert.ToDouble(oHeight)));

  }

  //生成缩略原图 

  Bitmap tImage = new Bitmap(tWidth, tHeight);

  Graphics g = Graphics.FromImage(tImage);

  g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; //设置高质量插值法 

  g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;//设置高质量,低速度呈现平滑程度 

  g.Clear(Color.Transparent); //清空画布并以透明背景色填充 

  g.DrawImage(oImage, new Rectangle(0, 0, tWidth, tHeight), new Rectangle(0, 0, oWidth, oHeight), GraphicsUnit.Pixel);

  string oFullName = Server.MapPath(".") + "/image/" + "o" + DateTime.Now.ToShortDateString().Replace("-", "") + DateTime.Now.Hour.ToString() + DateTime.Now.Minute.ToString() + DateTime.Now.Second.ToString() + DateTime.Now.Millisecond.ToString() + ".jpg"; //保存原图的物理路径 

  string tFullName = Server.MapPath(".") + "/image/" + "t" + DateTime.Now.ToShortDateString().Replace("-", "") + DateTime.Now.Hour.ToString() + DateTime.Now.Minute.ToString() + DateTime.Now.Second.ToString() + DateTime.Now.Millisecond.ToString() + ".jpg"; //保存缩略图的物理路径 

  try

  {

   //以JPG格式保存图片 

   oImage.Save(oFullName, System.Drawing.Imaging.ImageFormat.Jpeg);

   tImage.Save(tFullName, System.Drawing.Imaging.ImageFormat.Jpeg);

  }

  catch (Exception ex)

  {

   throw ex;

  }

  finally

  {

   //释放资源 

   oImage.Dispose();

   g.Dispose();

   tImage.Dispose();

  }

 }

}







这里再补充一个改进方法：





#region 上传图片 并生成缩略图

/// <summary>

/// 上传图片生成缩略图

/// </summary>

/// <param name="originalImagePath">图片源路径</param>

/// <param name="thumbnailPath">缩略图路径(物理路径)</param>

/// <param name="width">缩略图宽度</param>

/// <param name="height">缩略图高度</param>

/// <param name="mode">生成缩略图的方式</param>

public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode) {

  //从路径中获取源图片的文件

  System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);

  int towidth = width;

  int toheight = height;

  int x = 0;

   int y = 0;

  //获取图片的宽度

   int ow = image.Width;

  //获取图片的高度

   int oh = image.Height;

  //生成缩略图的方式

   switch (mode) { 

    case "HW":

    break;

    case "W"://指定宽度 高按比例

    toheight = originalImage.Height * width / originalImage.Width;

    break;

    case "H"://指定图片的高度 宽按比例

    towidth = originalImage.Width * height / originalImage.Height;

    break;

    case "Cut"://如果为裁减模式 则不变形 

    if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)

    {

     oh = originalImage.Height;

     //缩略图片的宽度

     ow = originalImage.Height * towidth / toheight;

     y = 0;

     x = (originalImage.Width - ow) / 2;

    }

    else {

     ow = originalImage.Width;

     //缩略图片的高度

     oh = originalImage.Width * toheight / towidth;

     x = 0;

     y(originalImage.Height - oh) / 2;

    }

    break;

    default: break;

   }

  //新建一个bmp图片

   Bitmap bitmap = new Bitmap(towidth, toheight);

  //新建一个画布 以BitMap 宽 高作为画布的大小

   Graphics g = Graphics.FromImage(bitmap);

  //设置高质量插值法

   g.InterpolationMode = InterpolationMode.High;

  //以高质量 低速度 呈现

   g.SmoothingMode = SmoothingMode.HighQuality;

  //清空画布 以白色背景色填充 

   g.Clear(Color.Transparent);

   //在指定位置并且按指定大小绘制原图片的指定部分

   g.DrawImage(originalImage,new Rectangle(towidth,toheight),new Rectangle(x,y,ow,oh),GraphicsUnit.Pixel);

   try

   {

    //以jpg格式保存缩略图

    bitmap.Save(thumbnailPath,System.Drawing.Imaging.ImageFormat.Jpeg);

   }

   catch (Exception ex)

   {

    throw ex;

   }

   finally {

    //释放资源

    originalImage.Dispose();

    bitmap.Dispose();

    g.Dispose();

   }

}

#endregion







希望本文所述对大家asp.net程序设计有所帮助。