根據文件夾路徑，壓縮超過指定大小的圖片，並上傳到指定路徑

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;

namespace FolderImage
{
    /// <summary>
    /// 根據文件夾路徑，查看下面有哪些圖片，若是超過了指定的大小，則壓縮圖片，上傳到指定的路徑
    /// </summary>
    public static class ImageFolderHelper
    {
        //文件夾下面的全部圖片路徑
        public static List<string> imageList = new List<string>();
        /// <summary>
        /// 獲取文件夾下面的文件
        /// </summary>
        public static void ImageFileList(string path = @"E:\測試\inetshop")
        {
            DirectoryInfo root = new DirectoryInfo(path);
            //獲取文件夾下面的文件
            FileInfo[] files = root.GetFiles();
            foreach (FileInfo fi in files)
            {
                if (fi.Extension == ".jpg" || fi.Extension == ".gif" || fi.Extension == ".png" || fi.Extension == ".jpeg")
                {
                    // 寫你本身的處理代碼
                    imageList.Add(fi.FullName);
                    ImageByte(fi.FullName);
                }
            }
            //獲取文件夾下面的子文件夾
            DirectoryInfo[] dics = root.GetDirectories();
            foreach (var item in dics)
            {
                ImageFileList(item.FullName);
            }
        }

        /// <summary>
        /// 根據圖片大小看是否壓縮從新上傳
        /// </summary>
        /// <param name="ImageFile">圖片路徑</param>
        public static void ImageByte(string ImageFile)
        {
            var imagebyte = GetImageByteIam(ImageFile);

            //讀入MemoryStream對象  
            using (Stream sr = new MemoryStream(imagebyte))
            {
                //超過1M就壓縮
                if (sr.Length > 1 * 1024 * 1024)
                {
                    CompressImage(ImageFile, ImageFile.Replace("inetshop", "backshop"));
                }
            }
        }

        /// <summary>
        /// 根據本機圖片路徑返回圖片的字節流byte[]
        /// </summary>
        /// <param name="imagePath">圖片路徑</param>
        public static byte[] GetImageByteIam(string imagePath)
        {
            FileStream files = new FileStream(imagePath, FileMode.Open);
            byte[] imgByte = new byte[files.Length];
            files.Read(imgByte, 0, imgByte.Length);
            files.Close();
            return imgByte;
        }

        /// <summary>
        /// 無損壓縮圖片
        /// </summary>
        /// <param name="sFile">原圖片地址</param>
        /// <param name="dFile">壓縮後保存圖片地址</param>
        /// <param name="flag">壓縮質量（數字越小壓縮率越高）1-100</param>
        /// <param name="size">壓縮後圖片的最大大小</param>
        /// <param name="sfsc">是不是第一次調用</param>
        /// <returns></returns>
        public static bool CompressImage(string sFile, string dFile, int flag = 50, int size = 512, bool sfsc = true)
        {
            //是否存在文件夾
            var index = dFile.LastIndexOf('\\');
            var sfilestring = dFile.Substring(0, index);
            if (!Directory.Exists(sfilestring))
            {
                //建立
                DirectoryInfo directoryInfo = new DirectoryInfo(sfilestring);
                directoryInfo.Create();
            }

            //若是是第一次調用，原始圖像的大小小於要壓縮的大小，則直接複製文件，而且返回true
            FileInfo firstFileInfo = new FileInfo(sFile);
            if (sfsc == true && firstFileInfo.Length < size * 1024)
            {
                firstFileInfo.CopyTo(dFile);
                return true;
            }
            System.Drawing.Image iSource = System.Drawing.Image.FromFile(sFile);
            ImageFormat tFormat = iSource.RawFormat;
            int dHeight = iSource.Height / 2;
            int dWidth = iSource.Width / 2;
            int sW = 0, sH = 0;
            //按比例縮放
            Size tem_size = new Size(iSource.Width, iSource.Height);
            if (tem_size.Width > dHeight || tem_size.Width > dWidth)
            {
                if ((tem_size.Width * dHeight) > (tem_size.Width * dWidth))
                {
                    sW = dWidth;
                    sH = (dWidth * tem_size.Height) / tem_size.Width;
                }
                else
                {
                    sH = dHeight;
                    sW = (tem_size.Width * dHeight) / tem_size.Height;
                }
            }
            else
            {
                sW = tem_size.Width;
                sH = tem_size.Height;
            }

            Bitmap ob = new Bitmap(dWidth, dHeight);
            Graphics g = Graphics.FromImage(ob);

            g.Clear(Color.WhiteSmoke);
            g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;

            g.DrawImage(iSource, new Rectangle((dWidth - sW) / 2, (dHeight - sH) / 2, sW, sH), 0, 0, iSource.Width, iSource.Height, GraphicsUnit.Pixel);

            g.Dispose();

            //如下代碼爲保存圖片時，設置壓縮質量
            EncoderParameters ep = new EncoderParameters();
            long[] qy = new long[1];
            qy[0] = flag;//設置壓縮的比例1-100
            EncoderParameter eParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qy);
            ep.Param[0] = eParam;

            try
            {
                ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();
                ImageCodecInfo jpegICIinfo = null;
                for (int x = 0; x < arrayICI.Length; x++)
                {
                    if (arrayICI[x].FormatDescription.Equals("JPEG"))
                    {
                        jpegICIinfo = arrayICI[x];
                        break;
                    }
                }
                if (jpegICIinfo != null)
                {
                    ob.Save(dFile, jpegICIinfo, ep);//dFile是壓縮後的新路徑
                    FileInfo fi = new FileInfo(dFile);
                    if (fi.Length > 1024 * size)
                    {
                        flag = flag - 10;
                        CompressImage(sFile, dFile, flag, size, false);
                    }
                }
                else
                {
                    ob.Save(dFile, tFormat);
                }
                return true;
            }
            catch (Exception ex)
            {
                return false;
            }
            finally
            {
                iSource.Dispose();
                ob.Dispose();
            }
        }
    }
   
}