缩略图 

 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            Image originalImage = Image.FromFile(originalImagePath); 
12             
13            int towidth = width; 
14            int toheight = height; 
15         
16            int x = 0; 
17            int y = 0; 
18            int ow = originalImage.Width; 
19            int oh = originalImage.Height;         
20 
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            }     
50             
51            //新建一个bmp图片 
52            Image bitmap = new System.Drawing.Bitmap(towidth,toheight); 
53 
54            //新建一个画板 
55            Graphics g = System.Drawing.Graphics.FromImage(bitmap); 
56 
57            //设置高质量插值法 
58            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; 
59 
60            //设置高质量,低速度呈现平滑程度 
61            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; 
62 
63            //清空画布并以透明背景色填充 
64            g.Clear(Color.Transparent);         
65 
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 Rectangle(0, 0, towidth, toheight), 
68                new Rectangle(x, y, ow,oh), 
69                GraphicsUnit.Pixel); 
70 
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        }

 

posted @ 2019-06-29 23:32  陈彦斌  阅读(236)  评论(0)    收藏  举报