01.        //
02.        /// 生成缩略图
03.        ///
04.        /// 源图路径
05.        /// 缩略图路径
06.        /// 缩略图宽度
07.        /// 缩略图高度
08.        /// 生成缩略图的方式:HW指定高宽缩放(可能变形);W指定宽，高按比例 H指定高，宽按比例 Cut指定高宽裁减(不变形)　　
09.        /// 要缩略图保存的格式(gif,jpg,bmp,png) 为空或未知类型都视为jpg　　
10.        public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode, string imageType)
11.        {
12.            Image originalImage = Image.FromFile(originalImagePath);
13.            int towidth = width;
14.            int toheight = height;
15.            int x = 0;
16.            int y = 0;
17.            int ow = originalImage.Width;
18.            int oh = originalImage.Height;
19.20.            switch (mode)
21.            {
22.                case "HW"://指定高宽缩放（可能变形）　　　　　　　　
23.                    break;
24.                case "W"://指定宽，高按比例　　　　　　　　　　
25.                    toheight = originalImage.Height * width / originalImage.Width;
26.                    break;
27.                case "H"://指定高，宽按比例
28.                    towidth = originalImage.Width * height / originalImage.Height;
29.                    break;
30.                case "Cut"://指定高宽裁减（不变形）　　　　　　　　
31.                    if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
32.                    {
33.                        oh = originalImage.Height;
34.                        ow = originalImage.Height * towidth / toheight;
35.                        y = 0;
36.                        x = (originalImage.Width - ow) / 2;
37.                    }
38.                    else
39.                    {
40.                        ow = originalImage.Width;
41.                        oh = originalImage.Width * height / towidth;
42.                        x = 0;
43.                        y = (originalImage.Height - oh) / 2;
44.                    }
45.                    break;
46.                default:
47.                    break;
48.            }
49.            //新建一个bmp图片
50.            Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
51.52.            //新建一个画板
53.            Graphics g = System.Drawing.Graphics.FromImage(bitmap);
54.55.            //设置高质量插值法
56.            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
57.58.            //设置高质量,低速度呈现平滑程度
59.            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
60.61.            //清空画布并以透明背景色填充
62.            g.Clear(Color.Transparent);
63.64.            //在指定位置并且按指定大小绘制原图片的指定部分
65.            g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight),
66.              new Rectangle(x, y, ow, oh),
67.              GraphicsUnit.Pixel);
68.69.            try
70.            {
71.                //以jpg格式保存缩略图
72.                switch (imageType.ToLower())
73.                {
74.                    case "gif":
75.                        bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Gif);
76.                        break;
77.                    case "jpg":
78.                        bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
79.                        break;
80.                    case "bmp":
81.                        bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Bmp);
82.                        break;
83.                    case "png":
84.                        bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Png);
85.                        break;
86.                    default:
87.                        bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
88.                        break;
89.                }
90.            }
91.            catch (System.Exception e)
92.            {
93.                throw e;
94.            }
95.            finally
96.            {
97.                originalImage.Dispose();
98.                bitmap.Dispose();
99.                g.Dispose();
100.            }
101.        }