笔记

        今天看到了一个处理图片的类中有一个得到图片的缩略图的方法，没想到C#中处理图片是这样的简单。

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 "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） </param>    
9.         public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
10.         {
11.             System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);
13.             int towidth = width;
14.             int toheight = height;
16.             int x = 0;
17.             int y = 0;
18.             int ow = originalImage.Width;
19.             int oh = originalImage.Height;
21.             switch (mode)
22.             {
23.                 case "HW"://指定高宽缩放（可能变形）                
24.                     break;
25.                 case "W"://指定宽，高按比例                    
26.                     toheight = originalImage.Height * width / originalImage.Width;
27.                     break;
28.                 case "H"://指定高，宽按比例
29.                     towidth = originalImage.Width * height / originalImage.Height;
30.                     break;
31.                 case "Cut"://指定高宽裁减（不变形）                
32.                     if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
33.                     {
34.                         oh = originalImage.Height;
35.                         ow = originalImage.Height * towidth / toheight;
36.                         y = 0;
37.                         x = (originalImage.Width - ow) / 2;
38.                     }
39.                     else
40.                     {
41.                         ow = originalImage.Width;
42.                         oh = originalImage.Width * height / towidth;
43.                         x = 0;
44.                         y = (originalImage.Height - oh) / 2;
45.                     }
46.                     break;
47.                 default:
48.                     break;
49.             }
51.             //新建一个bmp图片
52.             System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
54.             //新建一个画板
55.             System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);
57.             //设置高质量插值法
58.             g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
60.             //设置高质量,低速度呈现平滑程度
61.             g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
63.             //清空画布并以透明背景色填充
64.             g.Clear(System.Drawing.Color.Transparent);
66.             //在指定位置并且按指定大小绘制原图片的指定部分
67.             g.DrawImage(originalImage, new System.Drawing.Rectangle(0, 0, towidth, toheight),
68.                 new System.Drawing.Rectangle(x, y, ow, oh),
69.                 System.Drawing.GraphicsUnit.Pixel);
71.             try
72.             {
73.                 //以jpg格式保存缩略图
74.                 bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
75.             }
76.             catch (System.Exception e)
77.             {
78.                 throw e;
79.             }
80.             finally
81.             {
82.                 originalImage.Dispose();
83.                 bitmap.Dispose();
84.                 g.Dispose();
85.             }
86.         }