/// <summary>
/// 获取一个图片按等比例缩小后的大小。
/// </summary>
/// <param name="maxWidth">需要缩小到的宽度</param>
/// <param name="maxHeight">需要缩小到的高度</param>
/// <param name="imageOriginalWidth">图片的原始宽度</param>
/// <param name="imageOriginalHeight">图片的原始高度</param>
/// <returns>返回图片按等比例缩小后的实际大小</returns>
public static Size GetNewSize(int maxWidth, int maxHeight, int imageOriginalWidth, int imageOriginalHeight)
{
  double w = 0.0;
  double h = 0.0;
  double sw = Convert.ToDouble(imageOriginalWidth);
  double sh = Convert.ToDouble(imageOriginalHeight);
  double mw = Convert.ToDouble(maxWidth);
  double mh = Convert.ToDouble(maxHeight);
  if (sw < mw && sh < mh)
  {
    w = sw;
    h = sh;
  }
  else if ((sw / sh) > (mw / mh))
  {
    w = maxWidth;
    h = (w * sh) / sw;
  }
  else
  {
    h = maxHeight;
    w = (h * sw) / sh;
  }
  return new Size(Convert.ToInt32(w), Convert.ToInt32(h));
}
/// <summary>
/// 对给定的一个图片（Image对象）生成一个指定大小的缩略图。
/// </summary>
/// <param name="originalImage">原始图片</param>
/// <param name="thumMaxWidth">缩略图的宽度</param>
/// <param name="thumMaxHeight">缩略图的高度</param>
/// <returns>返回缩略图的Image对象</returns>
public static System.Drawing.Image GetThumbNailImage(System.Drawing.Image originalImage, int thumMaxWidth, int thumMaxHeight)
{
  Size thumRealSize = Size.Empty;
  System.Drawing.Image newImage = originalImage;
  Graphics graphics = null;
  try
  {
    thumRealSize = GetNewSize(thumMaxWidth, thumMaxHeight, originalImage.Width, originalImage.Height);
    newImage = new Bitmap(thumRealSize.Width, thumRealSize.Height);
    graphics = Graphics.FromImage(newImage);
    graphics.CompositingQuality = CompositingQuality.HighQuality;
    graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
    graphics.SmoothingMode = SmoothingMode.HighQuality;
    graphics.Clear(Color.Transparent);
    graphics.DrawImage(originalImage, new Rectangle(0, 0, thumRealSize.Width, thumRealSize.Height), new Rectangle(0, 0, originalImage.Width, originalImage.Height), GraphicsUnit.Pixel);
  }
  catch { }
  finally
  {
    if (graphics != null)
    {
      graphics.Dispose();
      graphics = null;
    }
  }
  return newImage;
}
/// <summary>
/// 对给定的一个图片文件生成一个指定大小的缩略图。
/// </summary>
/// <param name="originalImage">图片的物理文件地址</param>
/// <param name="thumMaxWidth">缩略图的宽度</param>
/// <param name="thumMaxHeight">缩略图的高度</param>
/// <returns>返回缩略图的Image对象</returns>
public static System.Drawing.Image GetThumbNailImage(string imageFile, int thumMaxWidth, int thumMaxHeight)
{
  System.Drawing.Image originalImage = null;
  System.Drawing.Image newImage = null;
  try
  {
    originalImage = System.Drawing.Image.FromFile(imageFile);
    newImage = GetThumbNailImage(originalImage, thumMaxWidth, thumMaxHeight);
  }
  catch { }
  finally
  {
    if (originalImage != null)
    {
      originalImage.Dispose();
      originalImage = null;
    }
  }
  return newImage;
}
/// <summary>
/// 对给定的一个图片文件生成一个指定大小的缩略图，并将缩略图保存到指定位置。
/// </summary>
/// <param name="originalImageFile">图片的物理文件地址</param>
/// <param name="thumbNailImageFile">缩略图的物理文件地址</param>
/// <param name="thumMaxWidth">缩略图的宽度</param>
/// <param name="thumMaxHeight">缩略图的高度</param>
public static void MakeThumbNail(string originalImageFile, string thumbNailImageFile, int thumMaxWidth, int thumMaxHeight)
{
  System.Drawing.Image newImage = GetThumbNailImage(originalImageFile, thumMaxWidth, thumMaxHeight);
  try
  {
    newImage.Save(thumbNailImageFile, ImageFormat.Jpeg);
  }
  catch
  { }
  finally
  {
    newImage.Dispose();
    newImage = null;
  }
}
/// <summary>
/// 将一个图片的内存流调整为指定大小，并返回调整后的内存流。
/// </summary>
/// <param name="originalImageStream">原始图片的内存流</param>
/// <param name="newWidth">新图片的宽度</param>
/// <param name="newHeight">新图片的高度</param>
/// <returns>返回调整后的图片的内存流</returns>
public static MemoryStream ResizeImage(Stream originalImageStream, int newWidth, int newHeight)
{
  MemoryStream newImageStream = null;
  System.Drawing.Image newImage = Globals.GetThumbNailImage(System.Drawing.Image.FromStream(originalImageStream), newWidth, newHeight);
  if (newImage != null)
  {
    newImageStream = new MemoryStream();
    newImage.Save(newImageStream, ImageFormat.Jpeg);
  }
  return newImageStream;
}
/// <summary>
/// 将一个内存流保存为磁盘文件。
/// </summary>
/// <param name="stream">内存流</param>
/// <param name="newFile">目标磁盘文件地址</param>
public static void SaveStreamToFile(Stream stream, string newFile)
{
  if (stream == null || stream.Length == 0 || string.IsNullOrEmpty(newFile))
  {
    return;
  }
  byte[] buffer = new byte[stream.Length];
  stream.Position = 0;
  stream.Read(buffer, 0, buffer.Length);
  FileStream fileStream = new FileStream(newFile, FileMode.OpenOrCreate, FileAccess.Write);
  fileStream.Write(buffer, 0, buffer.Length);
  fileStream.Flush();
  fileStream.Close();
  fileStream.Dispose();
}
/// <summary>
/// 对一个指定的图片加上图片水印效果。
/// </summary>
/// <param name="imageFile">图片文件地址</param>
/// <param name="waterImage">水印图片（Image对象）</param>
public static void CreateImageWaterMark(string imageFile, System.Drawing.Image waterImage)
{
  if (string.IsNullOrEmpty(imageFile) || !File.Exists(imageFile) || waterImage == null)
  {
    return;
  }
  System.Drawing.Image originalImage = System.Drawing.Image.FromFile(imageFile);
  if (originalImage.Width - 10 < waterImage.Width || originalImage.Height - 10 < waterImage.Height)
  {
    return;
  }
  Graphics graphics = Graphics.FromImage(originalImage);
  int x = originalImage.Width - waterImage.Width - 10;
  int y = originalImage.Height - waterImage.Height - 10;
  int width = waterImage.Width;
  int height = waterImage.Height;
  graphics.DrawImage(waterImage, new Rectangle(x, y, width, height), 0, 0, width, height, GraphicsUnit.Pixel);
  graphics.Dispose();
  MemoryStream stream = new MemoryStream();
  originalImage.Save(stream, ImageFormat.Jpeg);
  originalImage.Dispose();
  System.Drawing.Image imageWithWater = System.Drawing.Image.FromStream(stream);
  imageWithWater.Save(imageFile);
  imageWithWater.Dispose();
}
/// <summary>
/// 对一个指定的图片加上文字水印效果。
/// </summary>
/// <param name="imageFile">图片文件地址</param>
/// <param name="waterText">水印文字内容</param>
public static void CreateTextWaterMark(string imageFile, string waterText)
{
  if (string.IsNullOrEmpty(imageFile) || string.IsNullOrEmpty(waterText) || !File.Exists(imageFile))
  {
    return;
  }
  System.Drawing.Image originalImage = System.Drawing.Image.FromFile(imageFile);
  Graphics graphics = Graphics.FromImage(originalImage);
  graphics.SmoothingMode = SmoothingMode.HighQuality;
  graphics.TextRenderingHint = TextRenderingHint.ClearTypeGridFit;
  graphics.CompositingQuality = CompositingQuality.HighQuality;
  graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
  SolidBrush brush = new SolidBrush(Color.FromArgb(153, 255, 255, 255));
  Font waterTextFont = new Font("Arial", 16, FontStyle.Regular);
  SizeF waterTextSize = graphics.MeasureString(waterText, waterTextFont);
  float x = (float)originalImage.Width - waterTextSize.Width - 10F;
  float y = (float)originalImage.Height - waterTextSize.Height - 10F;
  graphics.DrawString(waterText, waterTextFont, brush, x, y);
  graphics.Dispose();
  brush.Dispose();
  MemoryStream stream = new MemoryStream();
  originalImage.Save(stream, ImageFormat.Jpeg);
  originalImage.Dispose();
  System.Drawing.Image imageWithWater = System.Drawing.Image.FromStream(stream);
  imageWithWater.Save(imageFile);
  imageWithWater.Dispose();
}
/// <summary>
/// 判断上传组件是否包含内容。
/// </summary>
/// <param name="fileUpload">ASP.NET 2.0标准上传组件</param>
/// <returns>如果数据有效，则返回True，否则返回False</returns>
public static bool IsAttachmentValid(FileUpload fileUpload)
{
  if (fileUpload != null &&
    fileUpload.PostedFile != null &&
    !string.IsNullOrEmpty(fileUpload.PostedFile.FileName) &&
    fileUpload.PostedFile.ContentLength > 0)
  {
    return true;
  }
  return false;
}

public class ImageHelper
{
  #region " 水印存放的相对路径 "
  public static string GetLogoPath()
  {
    return "/images/logo.png";  ///水印图路径
  }
  #endregion
  #region " 图片水印 "
  // <summary>
  // 在图片上生成图片水印,此方法不支持Gif类型的图片
  // </summary>
  // <param name="Path">原服务器图片路径</param>
  // <param name="Path_syp">生成的带图片水印的图片路径</param>
  // <param name="Path_sypf">水印图片路径</param>
  public static void MarkImage(Stream InUploadImagePath, string inLogoImagePath, string InSavePath)
  {
    System.Drawing.Image Image = System.Drawing.Image.FromStream(InUploadImagePath);
    System.Drawing.Image newimage = Image.FromFile(Current.Server.MapPath(inLogoImagePath));
    Graphics g = Graphics.FromImage(Image);
    g.DrawImage(newimage, new Rectangle(Image.Width - newimage.Width, Image.Height - newimage.Height, newimage.Width, newimage.Height), 0, 0, newimage.Width, newimage.Height, GraphicsUnit.Pixel);
    try {
      Image.Save(Current.Server.MapPath(InSavePath));
    }
    catch (Exception ex) {
    }
    finally {
      g.Dispose();
      Image.Dispose();
      newimage.Dispose();
    }
  }
  #endregion
}