C#圖片無損壓縮

項目中常常用到圖片的大小太大，這就須要圖片的無損壓縮。具體實現的代碼以下：

首先引用一下命名空間：

1 using System.Drawing.Imaging; 
2 using System.Drawing; 
3 using System.Drawing.Drawing2D;

實現方法：

 1     #region GetPicThumbnail
 2     /// <summary>
 3     /// 無損壓縮圖片
 4     /// </summary>
 5     /// <param name="sFile">原圖片</param>
 6     /// <param name="dFile">壓縮後保存位置</param>
 7     /// <param name="dHeight">高度</param>
 8     /// <param name="dWidth">寬度</param>
 9     /// <param name="flag">壓縮質量 1-100</param>
10     /// <returns></returns>
11  
12     public bool GetPicThumbnail(string sFile, string dFile, int dHeight, int dWidth, int flag)
13     {
14         System.Drawing.Image iSource = System.Drawing.Image.FromFile(sFile);
15         ImageFormat tFormat = iSource.RawFormat;
16         int sW = 0, sH = 0;
17         //按比例縮放
18         Size tem_size = new Size(iSource.Width, iSource.Height);
19         if (tem_size.Width > dHeight || tem_size.Width > dWidth) //將**改爲c#中的或者操做符號
20         {
21             if ((tem_size.Width * dHeight) > (tem_size.Height * dWidth))
22             {
23                 sW = dWidth;
24                 sH = (dWidth * tem_size.Height) / tem_size.Width;
25             }
26             else
27             {
28                 sH = dHeight;
29                 sW = (tem_size.Width * dHeight) / tem_size.Height;
30             }
31         }
32         else
33         {
34             sW = tem_size.Width;
35             sH = tem_size.Height;
36         }
37  
38         Bitmap ob = new Bitmap(dWidth, dHeight);
39         Graphics g = Graphics.FromImage(ob);
40         g.Clear(Color.WhiteSmoke);
41         g.CompositingQuality = CompositingQuality.HighQuality;
42         g.SmoothingMode = SmoothingMode.HighQuality;
43         g.InterpolationMode = InterpolationMode.HighQualityBicubic;
44         g.DrawImage(iSource, new Rectangle((dWidth - sW) / 2, (dHeight - sH) / 2, sW, sH), 0, 0, iSource.Width, iSource.Height, GraphicsUnit.Pixel);
45         g.Dispose();
46         //如下代碼爲保存圖片時，設置壓縮質量
47         EncoderParameters ep = new EncoderParameters();
48         long[] qy = new long[1];
49         qy[0] = flag;//設置壓縮的比例1-100
50         EncoderParameter eParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qy);
51         ep.Param[0] = eParam;
52         try
53         {
54             ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();
55  
56             ImageCodecInfo jpegICIinfo = null;
57  
58             for (int x = 0; x < arrayICI.Length; x++)
59             {
60                 if (arrayICI[x].FormatDescription.Equals("JPEG"))
61                 {
62                     jpegICIinfo = arrayICI[x];
63                     break;
64                 }
65             }
66             if (jpegICIinfo != null)
67             {
68                 ob.Save(dFile, jpegICIinfo, ep);//dFile是壓縮後的新路徑
69             }
70             else
71             {
72                 ob.Save(dFile, tFormat);
73             }
74             return true;
75         }
76         catch
77         {
78             return false;
79         }
80         finally
81         {
82             iSource.Dispose();
83             ob.Dispose();
84  
85         }
86     }
87     #endregion