C#简单生成缩略图的要领

/// <summary> /// 生成缩略图 /// </summary> /// <param>源图路径（物理路径）</param> /// <param>缩略图路径（物理路径）</param> /// <param>缩略图宽度</param> /// <param>缩略图高度</param> /// <param>生成缩略图的方法</param> public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode) { Image originalImage = Image.FromFile(originalImagePath); 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"://指定高宽裁汰（不乱形） 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,低速度泛起平滑水平 g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; //清空画布并以透明配景色填充 g.Clear(Color.Transparent); //在指定位置并且按指定巨细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格局生存缩略图 bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg); } catch(System.Exception e) { throw e; } finally { originalImage.Dispose(); bitmap.Dispose(); g.Dispose(); } }