/// <summary> /// 生成jpg缩略图字节,本人的小软件中需要用到的功能，所以自己做了一个函数，和大家分享 /// 为什么要生成字节而不是文件，这是为了方便后续处理啦^_^ /// </summary> /// <param name="originalImagePath">原始路径</param> /// <param name="quality">质量0-100</param> /// <param name="width">宽度</param> /// <param name="height">高度</param> /// <param name="mode">模式：HW,W,H,Cut</param> /// <returns></returns> public static byte[] MakeJPGThumbnailBytes(string originalImagePath, long quality, int width, int height, string mode) { Image originalImage = Image.FromFile(originalImagePath); MemoryStream s = new MemoryStream(); int towidth = width; int toheight = height; int x = 0; int y = 0; int ow = originalImage.Width; int oh = originalImage.Height; switch (mode) { case "HW"://指定高宽缩放（可能变形） break; case "W"://指定宽，高按比例 toheight = originalImage.Height * width / originalImage.Width; break; case "H"://指定高，宽按比例 towidth = originalImage.Width * height / originalImage.Height; break; case "Cut"://指定高宽裁减（不变形） if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight) { oh = originalImage.Height; ow = originalImage.Height * towidth / toheight; y = 0; x = (originalImage.Width - ow) / 2; } else { ow = originalImage.Width; oh = originalImage.Width * height / towidth; x = 0; y = (originalImage.Height - oh) / 2; } break; default: break; } //新建一个bmp图片 Image bitmap = new System.Drawing.Bitmap(towidth, toheight); //新建一个画板 Graphics g = System.Drawing.Graphics.FromImage(bitmap); //设置高质量插值法 g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; //设置高质量,低速度呈现平滑程度 g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; //清空画布并以透明背景色填充 g.Clear(Color.Transparent); //在指定位置并且按指定大小绘制原图片的指定部分 g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight), new Rectangle(x, y, ow, oh), GraphicsUnit.Pixel); try { //以jpg格式保存缩略图 EncoderParameters eps = new EncoderParameters(1); EncoderParameter ep = new EncoderParameter(Encoder.Quality,quality); eps.Param[0] = ep; bitmap.Save(s, GetCodecInfo("image/jpeg"), eps); return s.GetBuffer(); } catch (System.Exception e) { throw e; } finally { originalImage.Dispose(); bitmap.Dispose(); s.Dispose(); g.Dispose(); } } /**/ /// <summary> /// 保存JPG时用 /// </summary> /// <param name="mimeType"></param> /// <returns>得到指定mimeType的ImageCodecInfo</returns> private static ImageCodecInfo GetCodecInfo(string mimeType) { ImageCodecInfo[] CodecInfo = ImageCodecInfo.GetImageEncoders(); foreach (ImageCodecInfo ici in CodecInfo) { if (ici.MimeType == mimeType) return ici; } return null; }