生成縮略圖是一個十分常用功能，找到了一個方法，重寫部分代碼，實用又好用，.net又一個生成縮略圖的方法，不變形

/// <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 GetHvtThumbnail(System.Drawing.Image image, int width, int height)   {     Bitmap m_hovertreeBmp = new Bitmap(width, height);     //從Bitmap創建一個System.Drawing.Graphics      Graphics m_HvtGr = Graphics.FromImage(m_hovertreeBmp);     //設置      m_HvtGr.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;     //下面這個也設成高質量      m_HvtGr.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;     //下面這個設成High      m_HvtGr.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      Rectangle rectDestination = new Rectangle(0, 0, width, height);     int m_width, m_height;     if (image.Width * height > image.Height * width)     {       m_height = image.Height;       m_width = (image.Height * width) / height;     }     else     {       m_width = image.Width;       m_height = (image.Width * height) / width;     }     m_HvtGr.DrawImage(image, rectDestination, 0, 0, m_width, m_height, GraphicsUnit.Pixel);     return m_hovertreeBmp;   }

C#縮略圖生成類，采用高質量插值法實現縮略圖生成，高質量,低速度呈現平滑程度，可以保持縮略圖縱橫比，在獲取縮略圖的時候一開始就根據百分比獲取圖片的尺寸、根據設定的大小返回圖片的大小，并高質量保存縮略圖圖片，為原圖片設置EncoderParameters 對象。

以下為類文件，建議保存文件名為：ImageHelper.cs

using System;using System.Collections.Generic;using System.Drawing;using System.Drawing.Imaging;namespace HtmlSnap{  public static class ImageHelper  {    /// 獲取縮略圖    public static Image GetThumbnailImage(Image image, int width, int height)    {      if (image == null || width < 1 || height < 1)        return null;      // 新建一個bmp圖片      Image bitmap = new System.Drawing.Bitmap(width, height);      // 新建一個畫板      using (Graphics g = System.Drawing.Graphics.FromImage(bitmap))      {        // 設置高質量插值法        g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;        // 設置高質量,低速度呈現平滑程度        g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;                // 高質量、低速度復合        g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;         // 清空畫布并以透明背景色填充        g.Clear(Color.Transparent);         // 在指定位置并且按指定大小繪制原圖片的指定部分        g.DrawImage(image, new Rectangle(0, 0, width, height),          new Rectangle(0, 0, image.Width, image.Height),          GraphicsUnit.Pixel);        return bitmap;      }    }    /// <summary>    /// 生成縮略圖，并保持縱橫比    /// </summary>    /// <returns>生成縮略圖后對象</returns>    public static Image GetThumbnailImageKeepRatio(Image image, int width, int height)    {      Size imageSize = GetImageSize(image, width, height);      return GetThumbnailImage(image, imageSize.Width, imageSize.Height);    }    /// <summary>    /// 根據百分比獲取圖片的尺寸    /// </summary>    public static Size GetImageSize(Image picture, int percent)    {      if (picture == null || percent < 1)        return Size.Empty;      int width = picture.Width * percent / 100;      int height = picture.Height * percent / 100;      return GetImageSize(picture, width, height);    }    /// <summary>    /// 根據設定的大小返回圖片的大小，考慮圖片長寬的比例問題    /// </summary>    public static Size GetImageSize(Image picture, int width, int height)    {      if (picture == null || width < 1 || height < 1)        return Size.Empty;      Size imageSize;      imageSize = new Size(width, height);      double heightRatio = (double)picture.Height / picture.Width;      double widthRatio = (double)picture.Width / picture.Height;      int desiredHeight = imageSize.Height;      int desiredWidth = imageSize.Width;      imageSize.Height = desiredHeight;      if (widthRatio > 0)        imageSize.Width = Convert.ToInt32(imageSize.Height * widthRatio);      if (imageSize.Width > desiredWidth)      {        imageSize.Width = desiredWidth;        imageSize.Height = Convert.ToInt32(imageSize.Width * heightRatio);      }      return imageSize;    }    /// <summary>    /// 獲取圖像編碼解碼器的所有相關信息    /// </summary>    /// <param name="mimeType">包含編碼解碼器的多用途網際郵件擴充協議 (MIME) 類型的字符串</param>    /// <returns>返回圖像編碼解碼器的所有相關信息</returns>    public static ImageCodecInfo GetCodecInfo(string mimeType)    {      ImageCodecInfo[] CodecInfo = ImageCodecInfo.GetImageEncoders();      foreach (ImageCodecInfo ici in CodecInfo)      {        if (ici.MimeType == mimeType) return ici;      }      return null;    }    public static ImageCodecInfo GetImageCodecInfo(ImageFormat format)    {      ImageCodecInfo[] encoders = ImageCodecInfo.GetImageEncoders();      foreach (ImageCodecInfo icf in encoders)      {        if (icf.FormatID == format.Guid)        {          return icf;        }      }      return null;    }    public static void SaveImage(Image image, string savePath, ImageFormat format)    {      SaveImage(image, savePath, GetImageCodecInfo(format));    }    /// <summary>    /// 高質量保存圖片    /// </summary>    private static void SaveImage(Image image, string savePath, ImageCodecInfo ici)    {      // 設置 原圖片 對象的 EncoderParameters 對象      EncoderParameters parms = new EncoderParameters(1);      EncoderParameter parm = new EncoderParameter(Encoder.Quality, ((long)95));      parms.Param[0] = parm;      image.Save(savePath, ici, parms);      parms.Dispose();    }  }}