ASP.NET中生成縮略圖的方法

ASP.NET中生成縮略圖，只需你給定要生成的圖片路徑,生成後存放的服務器路徑，生成方式，生成的尺寸，還有生成後的圖片類型，即可爲你生成合適的縮略圖。先必須導入 using System.Drawing;

代碼如下:

01. // <summary>
02. /// 生成縮略圖
03. /// </summary>
04. /// <param name="originalImagePath">源圖路徑</param>
05. /// <param name="thumbnailPath">縮略圖路徑</param>
06. /// <param name="width">縮略圖寬度</param>
07. /// <param name="height">縮略圖高度</param>
08. /// <param name="mode">生成縮略圖的方式:HW指定高寬縮放(可能變形);W指定寬，高按比例 H指定高，寬按比例 Cut指定高寬裁減(不變形)</param>　　
09. /// <param name="mode">要縮略圖保存的格式(gif,jpg,bmp,png) 爲空或未知類型都視爲jpg</param>　　
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"://指定高寬縮放（可能變形）　　　　　　　　
23. break;
24. case "W"://指定寬，高按比例　　　　　　　　　　
25. toheight = originalImage.Height * width / originalImage.Width;
26. break;
27. case "H"://指定高，寬按比例
28. towidth = originalImage.Width * height / originalImage.Height;
29. break;
30. case "Cut"://指定高寬裁減（不變形）　　　　　　　　
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. //新建一個bmp圖片
50. Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
51.52. //新建一個畫板
53. Graphics g = System.Drawing.Graphics.FromImage(bitmap);
54.55. //設置高質量插值法
56. g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
57.58. //設置高質量,低速度呈現平滑程度
59. g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
60.61. //清空畫布並以透明背景色填充
62. g.Clear(Color.Transparent);
63.64. //在指定位置並且按指定大小繪製原圖片的指定部分
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格式保存縮略圖
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. }