/// <summary>/// 無損壓縮圖片/// </summary>/// <param name="sFile">原圖片地址</param>/// <param name="dFile">壓縮后保存圖片地址</param>/// <param name="flag">壓縮質量（數字越小壓縮率越高）1-100</param>/// <param name="size">壓縮后圖片的最大大小</param>/// <param name="sfsc">是否是第一次調用</param>/// <returns></returns>public static bool CompressImage(string sFile, string dFile, int flag = 90, int size = 300, bool sfsc = true){ Image iSource = Image.FromFile(sFile); ImageFormat tFormat = iSource.RawFormat; //如果是第一次調用，原始圖像的大小小于要壓縮的大小，則直接復制文件，并且返回true FileInfo firstFileInfo = new FileInfo(sFile); if (sfsc == true && firstFileInfo.Length < size * 1024) { firstFileInfo.CopyTo(dFile); return true; } 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(); //以下代碼為保存圖片時，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是壓縮后的新路徑  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 { return false; } finally { iSource.Dispose(); ob.Dispose(); }}