C#压缩图片

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.IO;
using System.Linq;
using System.Web;

namespace Siia.CarParts.UI.Common
{
    public class ImageHelper
    {

        public static bool GetPicThumbnail(string sFile, string outPath, int flag)
        {
            string domainPath = HttpRuntime.AppDomainAppPath.ToString();
            string fileName = sFile.Split('/').Last();
            string filePath = Path.GetFullPath(domainPath + sFile);
            string zipPath = Path.GetFullPath(domainPath + outPath + "\\zip");

            byte[] bs = File.ReadAllBytes(filePath);
            double size = (bs.Length / 1024);
            if (size < 1024)
                return true;
            System.Drawing.Image iSource = System.Drawing.Image.FromFile(filePath);
            ImageFormat tFormat = iSource.RawFormat;
            //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)
                {
                  
                    if (!Directory.Exists(zipPath))
                    {
                        Directory.CreateDirectory(zipPath);
                    }
                    iSource.Save(zipPath+"\\"+fileName, jpegICIinfo, ep);//outPath是压缩后的新路径  
                }
                //else
                //{
                //    iSource.Save(outPath, tFormat);
                //}
                return true;
            }
            catch
            {
                return false;
            }
            finally
            {
                iSource.Dispose();
                iSource.Dispose();
                string sourceFile = zipPath + "\\" + fileName;
                //覆盖源文件  
                if (System.IO.File.Exists(sourceFile))
                {
                    System.IO.File.Copy(sourceFile, filePath, true);
                }
               
            }

        }


        /// <summary>
        /// 图像缩略图处理
        /// </summary>
        /// <param name="bytes">图像源数据</param>
        /// <param name="compression">压缩质量 1-100</param>
        /// <param name="thumbWidth">缩略图的宽</param>
        /// <param name="thumbHeight">缩略图的高</param>
        /// <returns></returns>
        public static byte[] ConvertToThumbnail(byte[] bytes, int compression = 100, int thumbWidth = 0, int thumbHeight = 0)
        {
            byte[] bs = null;
            try
            {
                if (bytes != null)
                {
                    using (MemoryStream ms = new MemoryStream(bytes))
                    {
                        using (Bitmap srcimg = new Bitmap(ms))
                        {
                            if (thumbWidth == 0 && thumbHeight == 0)
                            {
                                thumbWidth = srcimg.Width;
                                thumbHeight = srcimg.Height;
                            }
                            using (Bitmap dstimg = new Bitmap(thumbWidth, thumbHeight))//图片压缩质量
                            {
                                //从Bitmap创建一个System.Drawing.Graphics对象，用来绘制高质量的缩小图。
                                using (Graphics gr = Graphics.FromImage(dstimg))
                                {
                                    //把原始图像绘制成上面所设置宽高的缩小图
                                    Rectangle rectDestination = new Rectangle(0, 0, thumbWidth, thumbHeight);
                                    gr.Clear(Color.WhiteSmoke);
                                    gr.CompositingQuality = CompositingQuality.HighQuality;
                                    gr.SmoothingMode = SmoothingMode.HighQuality;
                                    gr.InterpolationMode = InterpolationMode.HighQualityBicubic;
                                    gr.DrawImage(srcimg, rectDestination, 0, 0, srcimg.Width, srcimg.Height, GraphicsUnit.Pixel);

                                    EncoderParameters ep = new EncoderParameters(1);
                                    ep.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, compression);//设置压缩的比例1-100
                                    ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();
                                    ImageCodecInfo jpegICIinfo = arrayICI.FirstOrDefault(t => t.FormatID == System.Drawing.Imaging.ImageFormat.Png.Guid);
                                    using (MemoryStream dstms = new MemoryStream())
                                    {
                                        if (jpegICIinfo != null)
                                        {
                                            dstimg.Save(dstms, jpegICIinfo, ep);
                                        }
                                        else
                                        {
                                            dstimg.Save(dstms, System.Drawing.Imaging.ImageFormat.Png);//保存到内存里
                                        }
                                        bs = new Byte[dstms.Length];
                                        dstms.Position = 0;
                                        dstms.Read(bs, 0, bs.Length);
                                    }
                                }
                            }
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                //LogManager.DefaultLogger.Error(LogConvert.ParseWebEx(ex), string.Concat("ConvertToThumbnail error.", thumbWidth, " ", thumbHeight));
            }
            return bs;
        }
    }
}