上传图片生成略缩图“最佳解决”

using System; using System.IO; using System.Drawing; using System.Drawing.Drawing2D; using System.Drawing.Imaging; using System.Drawing.Text; using System.Text.RegularExpressions; /// <summary> // 图片处理。 // http://www.hulaka.com/ // (c) 2008 Dao /// </summary> public class Image { /// <summary> /// 缩略模式。 /// </summary> public enum ThumbMode : byte { /// <summary> /// 完整模式 /// </summary> Full = 1, /// <summary> /// 最大尺寸 /// </summary> Max } /// <summary> /// 缩略图。 /// </summary> /// <param name="image">要缩略的图片</param> /// <param name="size">要缩放的尺寸</param> /// <param name="mode">缩略模式</param> /// <param name="contentAlignment">对齐方式</param> /// <returns>返回已经缩放的图片。</returns> public static Bitmap Thumbnail(Bitmap image, Size size, ThumbMode mode, ContentAlignment contentAlignment) { if (!size.IsEmpty && !image.Size.IsEmpty && !size.Equals(image.Size)) { //先取一个宽比例。 double scale = (double)image.Width / (double)size.Width; //缩略模式 switch (mode) { case ThumbMode.Full: if (image.Height > image.Width) scale = (double)image.Height / (double)size.Height; break; case ThumbMode.Max: if (image.Height / scale < size.Height) scale = (double)image.Height / (double)size.Height; break; } SizeF newSzie = new SizeF((float)(image.Width / scale), (float)(image.Height / scale)); Bitmap result = new Bitmap(size.Width, size.Height); using (Graphics g = Graphics.FromImage(result)) { g.FillRectangle(Brushes.White, new Rectangle(new Point(0, 0), size)); g.InterpolationMode = InterpolationMode.HighQualityBicubic; g.SmoothingMode = SmoothingMode.HighQuality; g.PixelOffsetMode = PixelOffsetMode.HighQuality; g.CompositingMode = CompositingMode.SourceOver; g.CompositingQuality = CompositingQuality.HighQuality; g.TextRenderingHint = TextRenderingHint.AntiAliasGridFit; //对齐方式 RectangleF destRect; switch (contentAlignment) { case ContentAlignment.TopCenter: destRect = new RectangleF(new PointF(-(float)((newSzie.Width - size.Width) * 0.5), 0), newSzie); break; case ContentAlignment.TopRight: destRect = new RectangleF(new PointF(-(float)(newSzie.Width - size.Width), 0), newSzie); break; case ContentAlignment.MiddleLeft: destRect = new RectangleF(new PointF(0, -(float)((newSzie.Height - size.Height) * 0.5)), newSzie); break; case ContentAlignment.MiddleCenter: destRect = new RectangleF(new PointF(-(float)((newSzie.Width - size.Width) * 0.5), -(float)((newSzie.Height - size.Height) * 0.5)), newSzie); break; case ContentAlignment.MiddleRight: destRect = new RectangleF(new PointF(-(float)(newSzie.Width - size.Width), -(float)((newSzie.Height - size.Height) * 0.5)), newSzie); break; case ContentAlignment.BottomLeft: destRect = new RectangleF(new PointF(0, -(float)(newSzie.Height - size.Height)), newSzie); break; case ContentAlignment.BottomCenter: destRect = new RectangleF(new PointF(-(float)((newSzie.Width - size.Width) * 0.5), -(float)(newSzie.Height - size.Height)), newSzie); break; case ContentAlignment.BottomRight: destRect = new RectangleF(new PointF(-(float)(newSzie.Width - size.Width), -(float)(newSzie.Height - size.Height)), newSzie); break; default: destRect = new RectangleF(new PointF(0, 0), newSzie); break; } g.DrawImage(image, destRect, new RectangleF(new PointF(0F, 0F), image.Size), GraphicsUnit.Pixel); image.Dispose(); } return result; } else return image; } /// <summary> /// 保存图片。 /// </summary> /// <param name="image">要保存的图片</param> /// <param name="quality">品质（1L~100L之间，数值越大品质越好）</param> /// <param name="filename">保存路径</param> public static void SaveIamge(Bitmap image, long quality, string filename) { using (EncoderParameters encoderParams = new EncoderParameters(1)) { using (EncoderParameter parameter = (encoderParams.Param[0] = new EncoderParameter(Encoder.Quality, quality))) { ImageCodecInfo encoder = null; //取得扩展名 string ext = Path.GetExtension(filename); if (string.IsNullOrEmpty(ext)) ext = ".jpg"; //根据扩展名得到解码、编码器 foreach (ImageCodecInfo codecInfo in ImageCodecInfo.GetImageEncoders()) { if (Regex.IsMatch(codecInfo.FilenameExtension, string.Format(@"(;|^)/*/{0}(;|$)", ext), RegexOptions.IgnoreCase)) { encoder = codecInfo; break; } } Directory.CreateDirectory(Path.GetDirectoryName(filename)); image.Save(filename, encoder, encoderParams); } } } /// <summary> /// 保存图片。 /// </summary> /// <param name="stream">要保存的流</param> /// <param name="quality">品质（1L~100L之间，数值越大品质越好）</param> /// <param name="filename">保存路径</param> public static void SaveIamge(Stream stream, long quality, string filename) { using (Bitmap bmpTemp = new Bitmap(stream)) { SaveIamge(bmpTemp, quality, filename); } } }

 

 调用方法如下：
 using (Bitmap bmpAvatar = Image.Thumbnail(new Bitmap(/*<流，FileUpload 控件的 PostedFile.InputStream 属性>*/), new Size(48, 48), Image.ThumbMode.Full, ContentAlignment.MiddleCenter)) { Image.SaveIamge(bmpAvatar, 95L, Server.MapPath("~/upfiles/Avatar.jpg")); }