C#实现的上传图片、保存图片、加水印、生成缩略图功能示例

<form method="POST" enctype="multipart/form-data" action="UploadImg.ashx">
  <table>
    <tr>
      <td>func：</td>
      <td><input type="text" name="func"/></td>
    </tr>
    <tr>
      <td>用户Id：</td>
      <td><input type="text" name="userId"/></td>
    </tr>
    <tr>
      <td>头像：</td>
      <td><input type="file" name="icon"/></td>
    </tr>
    <tr>
      <td>水印：</td>
      <td><input type="text" name="waterMark"/></td>
    </tr>
  </table>
  <input type="submit" value="提交"/>
</form>

private string UploadImage(HttpContext context)
{
  try
  {
    System.IO.Stream stream = context.Request.Files["icon"].InputStream;
    //返回的图片路径可以存储在数据库中
    string imageUrl = SaveImage(stream, "Icon", "蝈蝈");
    string thumbnailImageUrl = SaveThumbnailImage(stream, "Icon");
    string thumbnailImageUrlWithWatermark = SaveThumbnailImage(ConfigurationManager.AppSettings["AttachmentsDirectory"] + imageUrl, "Icon");
    return "上传成功！";
  }
  catch (Exception ex)
  {
    return "上传失败！";
  }
}
private string SaveImage(Stream stream, string folderName, string waterMark)
{
  try
  {
    string fileName = Guid.NewGuid() + ".jpg";
    string path = ConfigurationManager.AppSettings["AttachmentsDirectory"];
    path = Path.Combine(path, folderName + "\\" + DateTime.Now.Year + "\\" + DateTime.Now.Month + "\\" + DateTime.Now.Day + "\\");
    string imageUrl = "/" + folderName + "/" + DateTime.Now.Year + "/" + DateTime.Now.Month + "/" + DateTime.Now.Day + "/";
    if (!string.IsNullOrEmpty(waterMark))
    {
      Image imgSource = Image.FromStream(stream);
      AddWatermarkAndSave(path, fileName, waterMark, imgSource, imgSource.Height - 300, 10, Color.Red,
        new Font("宋体", 40));
    }
    else
    {
      byte[] buffer = new byte[stream.Length];
      stream.Read(buffer, 0, buffer.Length);
      if (!Directory.Exists(path))
      {
        Directory.CreateDirectory(path);
      }
      System.IO.FileStream fs = new System.IO.FileStream(path + fileName, System.IO.FileMode.OpenOrCreate,
        System.IO.FileAccess.Write);
      fs.Write(buffer, 0, buffer.Length);
      fs.Flush();
      fs.Close();
    }
    return imageUrl + fileName;
  }
  catch (Exception ex)
  {
    return "";
  }
}
private string SaveThumbnailImage(Stream stream, string folderName)
{
  try
  {
    string fileName = Guid.NewGuid() + ".jpg";
    string path = ConfigurationManager.AppSettings["AttachmentsDirectory"];
    path = Path.Combine(path, folderName + "\\" + DateTime.Now.Year + "\\" + DateTime.Now.Month + "\\" + DateTime.Now.Day + "\\");
    string imageUrl = "/" + folderName + "/" + DateTime.Now.Year + "/" + DateTime.Now.Month + "/" + DateTime.Now.Day + "/";
    System.Drawing.Image.GetThumbnailImageAbort myCallback = new System.Drawing.Image.GetThumbnailImageAbort(GetFalse);
    //数据源来自Stream
    Image image = System.Drawing.Bitmap.FromStream(stream);
    System.Drawing.Image thumbnailImage = image.GetThumbnailImage(64, 64, myCallback, IntPtr.Zero);
    thumbnailImage.Save(path + fileName);
    thumbnailImage.Dispose();
    return imageUrl + fileName;
  }
  catch (Exception ex)
  {
    return "";
  }
}
private string SaveThumbnailImage(string originalFileName, string folderName)
{
  try
  {
    string fileName = Guid.NewGuid() + ".jpg";
    string path = ConfigurationManager.AppSettings["AttachmentsDirectory"];
    path = Path.Combine(path, folderName + "\\" + DateTime.Now.Year + "\\" + DateTime.Now.Month + "\\" + DateTime.Now.Day + "\\");
    string imageUrl = "/" + folderName + "/" + DateTime.Now.Year + "/" + DateTime.Now.Month + "/" + DateTime.Now.Day + "/";
    System.Drawing.Image.GetThumbnailImageAbort myCallback = new System.Drawing.Image.GetThumbnailImageAbort(GetFalse);
    //数据源来自File
    Image image = System.Drawing.Bitmap.FromFile(originalFileName);
    System.Drawing.Image thumbnailImage = image.GetThumbnailImage(64, 64, myCallback, IntPtr.Zero);
    thumbnailImage.Save(path + fileName);
    thumbnailImage.Dispose();
    return imageUrl + fileName;
  }
  catch (Exception ex)
  {
    return "";
  }
}
private bool GetFalse()
{
  return false;
}
/// <summary>
/// 图片加文字水印
/// </summary>
/// <param name="fileName"> </param>
/// <param name="text">水印文字，如果是多行用分号隔开</param>
/// <param name="img">图片</param>
/// <param name="paddingTop">上边距</param>
/// <param name="paddingLeft">左边距</param>
/// <param name="textColor">文字颜色</param>
/// <param name="textFont">字体</param>
/// <param name="path">保存地址</param>
/// <returns></returns>
private bool AddWatermarkAndSave(string path, string fileName, string text, Image img,
      int paddingTop, int paddingLeft, Color textColor, Font textFont)
{
  text = text + ";" + "当前时间：" + DateTime.Now.ToString("yyyy-MM-dd HH:mm");
  if (!Directory.Exists(path))
  {
    Directory.CreateDirectory(path);
  }
  textFont = new Font("宋体", 19);
  Bitmap bm = new Bitmap(img);
  System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bm);
  System.Drawing.Brush b = new SolidBrush(textColor);
  string[] str = text.Split(';');
  for (int i = 0; i < str.Length; i++)
    g.DrawString(str[i], textFont, b, paddingLeft, paddingTop + 33 * i);
  g.Dispose();
  bm.Save(path + fileName, ImageFormat.Jpeg);
  bm.Dispose();
  return true;
}