C#实现图片压缩

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
          
            Console.WriteLine("开始压缩");
            var DefinitionPath = ConfigurationManager.AppSettings["DefinitionPath"];//高清图片保存的项目相对路径
            var ThumbnailPath = ConfigurationManager.AppSettings["ThumbnailPath"];//项目保存相对路径
            var file = Directory.GetFiles(DefinitionPath, "*.jpg");
            var file1 = Directory.GetFiles(DefinitionPath, "*.png");
            if (!System.IO.Directory.Exists(ThumbnailPath))
                System.IO.Directory.CreateDirectory(ThumbnailPath);
            #region 压缩图片
            foreach (var item in file)
            {
                string file2 = item.Substring(DefinitionPath.Length + 1);

                //string file =  item.Substring(DefinitionPath.Length);
                Console.WriteLine(file2);
                CompressImage(item, ThumbnailPath + @"\" + file2, 100, 300, true);
            }
            foreach (var item in file1)
            {
                string file2 = item.Substring(DefinitionPath.Length + 1);
             
                //string file =  item.Substring(DefinitionPath.Length);

                CompressImage(item, ThumbnailPath + @"\" + file2, 90, 300, true);
            }
            #endregion
            #region 不执行
            //var file = Directory.GetFiles(ThumbnailPath, "*.jpg");
            //var file1 = Directory.GetFiles(ThumbnailPath, "*.png");
            //foreach (var item in file)
            //{
            //    string file2 = item.Substring(ThumbnailPath.Length + 1);

            //    //string file =  item.Substring(DefinitionPath.Length);
            //    FileInfo fileInfo = new FileInfo(item);
            //    if (fileInfo.Length > 40960)
            //    {
            //        CompressImage(item, ThumbnailPath1 + @"\" + file2, 90, 300, true);
            //    }
            //}
            //foreach (var item in file1)
            //{
            //    string file2 = item.Substring(ThumbnailPath.Length + 1);

            //    //string file =  item.Substring(DefinitionPath.Length);
            //    FileInfo fileInfo = new FileInfo(item);
            //    if (fileInfo.Length > 40960)
            //    {
            //        CompressImage(item, ThumbnailPath1 + @"\" + file2, 90, 300, true);
            //    }
            //}
            #endregion



            Console.WriteLine("压缩完成");

            Console.ReadKey();
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="sFile">图片原本路径</param>
        /// <param name="dFile">压缩后的路径</param>
        /// <param name="flag"></param>
        /// <param name="size"></param>
        /// <param name="sfsc"></param>
        /// <returns></returns>
        public static bool CompressImage(string sFile, string dFile, int flag = 90, int size = 300, bool sfsc = true)
        {
            if (sfsc)
            {
                FileInfo firstFileInfo1 = new FileInfo(sFile);
                firstFileInfo1.CopyTo(dFile,true);

            }
            //如果是第一次调用，原始图像的大小小于要压缩的大小，则直接复制文件，并且返回true
            FileInfo firstFileInfo = new FileInfo(dFile);
            //string a = firstFileInfo.Length

            if (sfsc == true && firstFileInfo.Length < 40960 || flag == 0)
            {
                //firstFileInfo.CopyTo(dFile, true);
                return true;
            }

            Image iSource = Image.FromFile(sFile);
            ImageFormat tFormat = iSource.RawFormat;
            int dHeight = iSource.Height / 2;
            int dWidth = iSource.Width / 2;
            int sW = 0, sH = 0;
            //按比例缩放
            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();

            //以下代码为保存图片时，设置压缩质量
            EncoderParameters ep = new EncoderParameters();
            long[] qy = new long[1];
            qy[0] = flag;//设置压缩的比例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是压缩后的新路径
                    FileInfo fi = new FileInfo(dFile);
                    if (fi.Length > 40960)
                    {
                        flag = flag - 5;
                        if (flag >= 0)
                        {
                            CompressImage(sFile, dFile, flag, size, false);
                        }
                        else
                        {
                            ob.Save(dFile, tFormat);
                            Console.WriteLine(dFile);
                        }


                    }
                }
                else
                {
                    ob.Save(dFile, tFormat);
                    Console.WriteLine(dFile);
                }
                return true;
            }
            catch (Exception ex)
            {
                File.WriteAllText(@"D:\\Imgload.TXT", ex.ToString()); 
                return false;
            }
            finally
            {

                iSource.Dispose();
                ob.Dispose();
            }
        }
    }
}

这里使用的是画图，并非文件流