里面有4个重载方法,有直接返回Image对象的,有生成缩略图,并且保存到指定目录的!

using System.IO;

/// <summary>
 /// 图片处理类
 /// 1、生成缩略图片或按照比例改变图片的大小和画质
 /// 2、将生成的缩略图放到指定的目录下
 /// </summary>
 public class ImageClass
 {
  public Image ResourceImage;
  private int ImageWidth;
  private int ImageHeight;

  public string ErrMessage;

  /// <summary>
  /// 类的构造函数
  /// </summary>
  /// <param name="ImageFileName">图片文件的全路径名称</param>
  public ImageClass(string ImageFileName)
  {
      ResourceImage=Image.FromFile(ImageFileName);
   ErrMessage="";
  }

  public bool ThumbnailCallback()
  {
   return false;
  }

  /// <summary>
  /// 生成缩略图重载方法1，返回缩略图的Image对象
  /// </summary>
  /// <param name="Width">缩略图的宽度</param>
  /// <param name="Height">缩略图的高度</param>
  /// <returns>缩略图的Image对象</returns>
  public Image GetReducedImage(int Width,int Height)
  {
   try
   {
    Image ReducedImage;

    Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback);
    
    ReducedImage=ResourceImage.GetThumbnailImage(Width,Height,callb,IntPtr.Zero);
 
    return ReducedImage;
   }
   catch(Exception e)
   {
    ErrMessage=e.Message;
       return null;
   }
  }

  /// <summary>
  /// 生成缩略图重载方法2，将缩略图文件保存到指定的路径
  /// </summary>
  /// <param name="Width">缩略图的宽度</param>
  /// <param name="Height">缩略图的高度</param>
  /// <param name="targetFilePath">缩略图保存的全文件名，(带路径)，参数格式：D:\Images\filename.jpg</param>
  /// <returns>成功返回true，否则返回false</returns>
  public bool GetReducedImage(int Width,int Height,string targetFilePath)
  {
   try
   {
    Image ReducedImage;

    Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback);
    
    ReducedImage=ResourceImage.GetThumbnailImage(Width,Height,callb,IntPtr.Zero);
    ReducedImage.Save(@targetFilePath,ImageFormat.Jpeg);

    ReducedImage.Dispose();
 
    return true;
   }
   catch(Exception e)
   {
    ErrMessage=e.Message;
    return false;
   }
  }

  /// <summary>
  /// 生成缩略图重载方法3，返回缩略图的Image对象
  /// </summary>
  /// <param name="Percent">缩略图的宽度百分比 如：需要百分之80，就填0.8</param>  
  /// <returns>缩略图的Image对象</returns>
  public Image GetReducedImage(double Percent)
  {
   try
   {
    Image ReducedImage;

    Image.GetThumbnailImageAbort callb=new Image.GetThumbna