1 /// <summary>
2 /// 生成缩略图
3 /// </summary>
4 /// <param name="originalImagePath">源图路径（物理路径）</param>
5 /// <param name="thumbnailPath">缩略图路径（物理路径）</param>
6 /// <param name="width">缩略图宽度</param>
7 /// <param name="height">缩略图高度</param>
8 /// <param name="mode">生成缩略图的方式</param>
9 public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
10 {
11 originalImagePath = string.Format(@"{0}{1}\{2}", StrHelp.GetPhysicalPath(),
ConfigurationManager.AppSettings["UploadPath"],
originalImagePath);
12 thumbnailPath = string.Format(@"{0}{1}\{2}", StrHelp.GetPhysicalPath(), ConfigurationManager.AppSettings["UploadPath"], thumbnailPath);
13 System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);
14
15 int towidth = width;
16 int toheight = height;
17
18 int x = 0;
19 int y = 0;
20 int ow = originalImage.Width;
21 int oh = originalImage.Height;
22
23 switch (mode)
24 {
25 case "HW"://指定高宽缩放（可能变形）
26 break;
27 case "W"://指定宽，高按比例
28 if (originalImage.Width < width)
29 {
30 towidth = originalImage.Width;
31 toheight = originalImage.Height;
32 }
33 else
34 {
35 toheight = originalImage.Height * width / originalImage.Width;
36 }
37 break;
38 case "H"://指定高，宽按比例
39 if (originalImage.Height < height)
40 {
41 toheight = originalImage.Height;
42 towidth = originalImage.Width;
43 }
44 else
45 {
46 towidth = originalImage.Width * height / originalImage.Height;
47 }
48 break;
49 case "Cut"://指定高宽裁减（不变形）
50 if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
51 {
52 oh = originalImage.Height;
53 ow = originalImage.Height * towidth / toheight;
54 y = 0;
55 x = (originalImage.Width - ow) / 2;
56 }
57 else
58 {
59 ow = originalImage.Width;
60 oh = originalImage.Width * height / towidth;
61 x = 0;
62 y = (originalImage.Height - oh) / 2;
63 }
64 break;
65 default:
66 break;
67 }
68
69 //新建一个bmp图片
70 System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
71
72 //新建一个画板
73 System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);
74
75 //设置高质量插值法
76 g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
77
78 //设置高质量,低速度呈现平滑程度
79 g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
80
81 //清空画布并以透明背景色填充
82 g.Clear(System.Drawing.Color.Transparent);
83
84 //在指定位置并且按指定大小绘制原图片的指定部分
85 g.DrawImage(originalImage, new System.Drawing.Rectangle(0, 0, towidth, toheight),
86 new System.Drawing.Rectangle(x, y, ow, oh),
87 System.Drawing.GraphicsUnit.Pixel);
88
89 try
90 {
91 string Path = thumbnailPath.Substring(0, thumbnailPath.LastIndexOf('\\'));
92 if (!Directory.Exists(Path))
93 {
94 Directory.CreateDirectory(Path);
95 }
96
97 //以jpg格式保存缩略图
98 bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
99 }
100 catch (System.Exception e)
101 {
102 throw e;
103 }
104 finally
105 {
106 originalImage.Dispose();
107 bitmap.Dispose();
108 g.Dispose();
109 }
110 }
