C# 生成缩略图

using System;
using System.Collections.Generic;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Runtime.Serialization.Formatters.Binary;
using System.Text;
using System.Threading.Tasks;

namespace BFKR.Help.IMG
{
    /// <summary>
    /// 生成缩略图
    /// </summary>
    public class MakeThumbnailImg
    {
        public static readonly MakeThumbnailImg Instance = new MakeThumbnailImg();
        ///<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 void MakeThumbnail(string originalImagePath, string thumbnailPath, string mode, out string outthumbnailPath, int width=100, int height=100)
        public byte[] MakeThumbnail(byte[] fileByte, string mode = "Cut", int width = 100, int height = 100)
        {
            //Image originalImage = System.Drawing.Image.FromFile(originalImagePath);

            //MemoryStream memStream = new MemoryStream(fileByte);
            //BinaryFormatter binFormatter = new BinaryFormatter();
            //Image originalImage = (Image)binFormatter.Deserialize(memStream);

            Image originalImage = null;
            using (MemoryStream ms = new MemoryStream(fileByte))
            {
                ms.Write(fileByte, 0, fileByte.Length);
                originalImage = Image.FromStream(ms, true);
            }



            int towidth = width;
            int toheight = height;

            int x = 0;
            int y = 0;
            int ow = originalImage.Width;
            int oh = originalImage.Height;

            switch (mode)
            {
                case "HW"://指定高宽缩放（可能变形）                 
                    break;
                case "W"://指定宽，高按比例                     
                    toheight = originalImage.Height * width / originalImage.Width;
                    break;
                case "H"://指定高，宽按比例 
                    towidth = originalImage.Width * height / originalImage.Height;
                    break;
                case "Cut"://指定高宽裁减（不变形）                 
                    if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
                    {
                        oh = originalImage.Height;
                        ow = originalImage.Height * towidth / toheight;
                        y = 0;
                        x = (originalImage.Width - ow) / 2;
                    }
                    else
                    {
                        ow = originalImage.Width;
                        oh = originalImage.Width * height / towidth;
                        x = 0;
                        y = (originalImage.Height - oh) / 2;
                    }
                    break;
                default:
                    break;
            }

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

            //新建一个画板 
            Graphics g = 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(0, 0, towidth, toheight),
             new Rectangle(x, y, ow, oh),
             GraphicsUnit.Pixel);

            try
            {
                //以jpg格式保存缩略图 
                //bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
                MemoryStream ms = new MemoryStream();
                bitmap.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);

                return ms.ToArray();
            }
            catch (System.Exception e)
            {
                throw e;
            }
            finally
            {
                originalImage.Dispose();
                bitmap.Dispose();
                g.Dispose();
            }
        }
    }
}