1         public static Image FixedSize(Image imgPhoto, int Width, int Height)
 2         {
 3             
 4             int sourceWidth = imgPhoto.Width;
 5             int sourceHeight = imgPhoto.Height;
 6 
 7 
 8             int sourceX = 0;
 9             int sourceY = 0;
10             int destX = 0;
11             int destY = 0;
12 
13             float nPercent = 0;
14             float nPercentW = 0;
15             float nPercentH = 0;
16 
17             nPercentW = ((float)sourceWidth / (float)Width); // 源图片宽度:画布宽度
18             nPercentH = ((float)sourceHeight / (float)Height);
19 
20             int destWidth = 0; //缩放后的 宽度
21             int destHeight = 0;//缩放后的 高度
22 
23             if (sourceHeight <= Height && sourceWidth <= Width)
24             {
25                 destWidth = sourceWidth;
26                 destHeight = sourceHeight;
27 
28                      
29             }
30             else
31             {
32                 //高度比较大
33                 if (nPercentH > nPercentW)
34                 {
35                     nPercent = nPercentH;
36                 }
37                 else
38                 {
39                     nPercent = nPercentW;
40                 }
41 
42                 destWidth = (int)((float)sourceWidth / nPercent);
43                 destHeight = (int)((float)sourceHeight / nPercent);
44             }
45 
46             destX = (int)(((float)Width - (float)destWidth) / 2);  //图片x 坐标
47             destY = (int)(((float)Height - (float)destHeight) / 2);//图片y 坐标 
48             
49 
50 
51             Bitmap bmPhoto = new Bitmap(Width, Height, PixelFormat.Format24bppRgb);
52             bmPhoto.SetResolution(imgPhoto.HorizontalResolution, imgPhoto.VerticalResolution);
53 
54             Graphics grPhoto = Graphics.FromImage(bmPhoto);
55             grPhoto.Clear(Color.White);
56             grPhoto.InterpolationMode = InterpolationMode.HighQualityBicubic;
57 
58             grPhoto.DrawImage(imgPhoto,
59                 new Rectangle(destX, destY, destWidth, destHeight),///它指定所绘制图像的位置和大小。
60                 new Rectangle(sourceX, sourceY, sourceWidth, sourceHeight),///它指定 image 对象中要绘制的部分。
61                 GraphicsUnit.Pixel);///它指定 srcRect 参数所用的度量单位。
62 
63             grPhoto.Dispose();
64             return bmPhoto;
65         }