柯乐义图片压缩类，本类可以将图片按指定的宽和高生成缩略图，同时压缩文件，如果指定的高宽和原图一样则只压缩图片的大小不改变尺寸，还可以指定压缩的质量。
WinForm示例下载地址：
using System.Drawing;using System.Drawing.Drawing2D;using System.Drawing.Imaging;namespace Keleyi.Com.Framework
{ public class KeleyiThumbnail{#region SaveKeleyiThumbnail
/// <summary>/// 无损压缩图片方法/// </summary>/// <param name="sFile">原图片全名</param>/// <param name="dFile">压缩后保存文件全名，后缀请写.jpg</param>/// <param name="dHeight">压缩后的宽度</param>/// <param name="dWidth">压缩后的高度</param>/// <param name="flag">压缩质量 1-100</param>/// <returns>是否成功</returns>public static bool SaveKeleyiThumbnail(string sFile, string dFile, int dWidth, int dHeight, int flag){ Image iSource = Image.FromFile(sFile);ImageFormat tFormat = iSource.RawFormat;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.Height * 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 = CompositingQuality.HighQuality;g.SmoothingMode = SmoothingMode.HighQuality;g.InterpolationMode = 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1-100EncoderParameter 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}else{ ob.Save(dFile, tFormat);}return true;}catch{ return false;}finally{ iSource.Dispose();ob.Dispose();}}#endregion}}本文转载自柯乐义