C#图片辅助类，形成缩略图

完善一下别人的方法，成自己好用的工具

 using System.Drawing;
 using System.Drawing.Imaging;

 namespace GXNUQzzx.Tools.Utility
 {
     /// <summary>
     /// 图片缩放模式
     /// </summary>
     public enum ScaleMode
     {
         /// <summary>
         /// 指定高宽缩放（可能失真）
         /// </summary>
         Normal,

         /// <summary>
         /// 指定高，宽按比例
         /// </summary>
         Width,

         /// <summary>
         /// 指定宽，高按比例
         /// </summary>
         Height,

         /// <summary>
         /// 指定高宽裁减（不失真）
         /// </summary>
         Cut
     }

     /// <summary>
     /// 图片辅助类
     /// </summary>
     public static class ImageHelper
     {
         /// <summary>
         /// 生成缩略图
         /// </summary>
         /// <param name="originalImagePath">源图路径（物理路径）</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 GenerateThumbnail(string originalImagePath, string thumbnailPath, int width, int height, ScaleMode mode)
         {
             using (Image originalImage = Image.FromFile(originalImagePath))
             {
                 GenerateThumbnail(originalImage, thumbnailPath, width, height, mode);
             }
         }

         /// <summary>
         /// 生成缩略图
         /// </summary>
         /// <param name="originalImage">源图</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 GenerateThumbnail(Image originalImage, string thumbnailPath, int width, int height, ScaleMode mode)
         {
             using (Image image = GenerateThumbnail(originalImage, width, height, mode))
             {
                 image.Save(thumbnailPath, ImageFormat.Jpeg);
             }
         }

         /// <summary>
         /// 生成缩略图
         /// </summary>
         /// <param name="originalImage">源图</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>
         /// <returns>生成的缩略图</returns>
         public static Image GenerateThumbnail(Image originalImage, int width, int height, ScaleMode mode)
         {
             int towidth = width;
             int toheight = height;

             int x = ;
             int y = ;
             int ow = originalImage.Width;
             int oh = originalImage.Height;

             #region // 计算缩略图宽高
             switch (mode)
             {
                 default:
                 case ScaleMode.Normal: { break; }
                 case ScaleMode.Height:
                 {
                     toheight = originalImage.Height * width / originalImage.Width;
                     break;
                 }
                 case ScaleMode.Width:
                 {
                     towidth = originalImage.Width * height / originalImage.Height;
                     break;
                 }
                 case ScaleMode.Cut:
                 {
                     if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
                     {
                         oh = originalImage.Height;
                         ow = originalImage.Height * towidth / toheight;
                         y = ;
                         x = (originalImage.Width - ow) / ;
                     }
                     else
                     {
                         ow = originalImage.Width;
                         oh = originalImage.Width * height / towidth;
                         x = ;
                         y = (originalImage.Height - oh) / ;
                     }
                     break;
                 }
             }
             #endregion

             //新建一个bmp图片
             Image bitmap = new System.Drawing.Bitmap(towidth, toheight);

             //新建一个画板
             using (Graphics g = System.Drawing.Graphics.FromImage(bitmap))
             {
                 //设置高质量插值法
                 g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

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

                 //清空画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);
             }

             // 返回生成的缩略图
             return bitmap;
         }

         /// <summary>
         /// 按原像素比例生成一张新图片
         /// </summary>
         /// <param name="oldImagePath">源图片路径（物理路径）</param>
         /// <param name="newImagePath">新图片路径（物理路径）</param>
         public static void GenerateNewImage(string oldImagePath, string newImagePath)
         {
             using (Image originalImage = Image.FromFile(oldImagePath))
             {
                 GenerateNewImage(originalImage, newImagePath);
             }
         }

         /// <summary>
         /// 按原像素比例生成一张新图片
         /// </summary>
         /// <param name="oldImage">源图片</param>
         /// <param name="newImagePath">新图片路径（物理路径）</param>
         public static void GenerateNewImage(Image oldImage, string newImagePath)
         {
             using (Image image = GenerateNewImage(oldImage))
             {
                 image.Save(newImagePath, ImageFormat.Jpeg);
             }
         }

         /// <summary>
         /// 按原像素比例生成一张新图片
         /// </summary>
         /// <param name="oldImage">源图片</param>
         /// <returns>新图片</returns>
         public static Image GenerateNewImage(Image oldImage)
         {
             int width = oldImage.Width;
             int height = oldImage.Height;

             //新建一个bmp图片
             Image bitmap = new System.Drawing.Bitmap(width, height);

             //新建一个画板
             using (Graphics g = System.Drawing.Graphics.FromImage(bitmap))
             {
                 //设置高质量插值法
                 g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

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

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

                 //创建矩形
                 var rectangle = new Rectangle(, , width, height);

                 //在指定位置并且按指定大小绘制原图片的指定部分
                 g.DrawImage(oldImage, rectangle, rectangle, GraphicsUnit.Pixel);
             }

             // 返回新图片
             return bitmap;
         }
     }
 }