C#生成图片缩略图(2种思路)

 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), new Rectangle(x, y, ow,oh),GraphicsUnit.Pixel);68     try 69     {             70     　　//以jpg格式保存缩略图 71     　　bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg); 72     } 73     catch(System.Exception e) 74     { 75        throw e; 76     } 77     finally 78     { 79     　　originalImage.Dispose(); 80        bitmap.Dispose();                         81        g.Dispose(); 82     } 83  }84 85 ThumbnailClass

  1 using System.IO;  2 using System.Drawing;  3 using System.Drawing.Imaging;  4   5 /// <summary>  6 /// 图片处理类  7 /// 1、生成缩略图片或按照比例改变图片的大小和画质  8 /// 2、将生成的缩略图放到指定的目录下  9 /// </summary> 10 public class ImageClass 11 { 12     public Image ResourceImage; 13     PRivate int ImageWidth; 14     private int ImageHeight; 15  16     public string ErrMessage; 17  18     /// <summary> 19     /// 类的构造函数 20     /// </summary> 21     /// <param name="ImageFileName">图片文件的全路径名称</param> 22     public ImageClass(string ImageFileName) 23     { 24         ResourceImage=Image.FromFile(ImageFileName); 25      ErrMessage=""; 26     } 27  28     public bool ThumbnailCallback() 29     { 30      return false; 31     } 32  33     /// <summary> 34     /// 生成缩略图重载方法1，返回缩略图的Image对象 35     /// </summary> 36     /// <param name="Width">缩略图的宽度</param> 37     /// <param name="Height">缩略图的高度</param> 38     /// <returns>缩略图的Image对象</returns> 39     public Image GetReducedImage(int Width,int Height) 40     { 41      try 42      { 43       Image ReducedImage; 44  45       Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback);  46       47       ReducedImage=ResourceImage.GetThumbnailImage(Width,Height,callb,IntPtr.Zero); 48    49       return ReducedImage; 50      } 51      catch(Exception e) 52      { 53       ErrMessage=e.Message;  54          return null; 55      } 56     } 57  58     /// <summary> 59     /// 生成缩略图重载方法2，将缩略图文件保存到指定的路径 60     /// </summary> 61     /// <param name="Width">缩略图的宽度</param> 62     /// <param name="Height">缩略图的高度</param> 63     /// <param name="targetFilePath">缩略图保存的全文件名，(带路径)，参数格式：D:/Images/filename.jpg</param> 64     /// <returns>成功返回true，否则返回false</returns> 65     public bool GetReducedImage(int Width,int Height,string targetFilePath) 66     { 67      try 68      { 69       Image ReducedImage; 70  71       Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback);  72       73       ReducedImage=ResourceImage.GetThumbnailImage(Width,Height,callb,IntPtr.Zero); 74       ReducedImage.Save(@targetFilePath,ImageFormat.Jpeg); 75  76       ReducedImage.Dispose();  77    78       return true; 79      } 80      catch(Exception e) 81      { 82       ErrMessage=e.Message;  83       return false; 84      } 85     } 86  87     /// <summary> 88     /// 生成缩略图重载方法3，返回缩略图的Image对象 89     /// </summary> 90     /// <param name="Percent">缩略图的宽度百分比 如：需要百分之80，就填0.8</param>   91     /// <returns>缩略图的Image对象</returns> 92     public Image GetReducedImage(double Percent) 93     { 94      try 95      { 96       Image ReducedImage; 97  98       Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback); 99 100       ImageWidth=Convert.ToInt32(ResourceImage.Width*Percent);101       ImageHeight=Convert.ToInt32(ResourceImage.Width*Percent);102      103       ReducedImage=ResourceImage.GetThumbnailImage(ImageWidth,ImageHeight,callb,IntPtr.Zero);104   105       return ReducedImage;106      }107      catch(Exception e)108      {109       ErrMessage=e.Message; 110       return null;111      }112     }113 114     /// <summary>115     /// 生成缩略图重载方法4，返回缩略图的Image对象116     /// </summary>117     /// <param name="Percent">缩略图的宽度百分比 如：需要百分之80，就填0.8</param>  118     /// <param name="targetFilePath">缩略图保存的全文件名，(带路径)，参数格式：D:/Images/filename.jpg</param>119     /// <returns>成功返回true,否则返回false</returns>120     public bool GetReducedImage(double Percent,string targetFilePath)121     {122      try123      {124       Image ReducedImage;125 126       Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback);127 128       ImageWidth=Convert.ToInt32(ResourceImage.Width*Percent);129       ImageHeight=Convert.ToInt32(ResourceImage.Width*Percent);130      131       ReducedImage=ResourceImage.GetThumbnailImage(ImageWidth,ImageHeight,callb,IntPtr.Zero);132 133       ReducedImage.Save(@targetFilePath,ImageFormat.Jpeg);134 135       ReducedImage.Dispose(); 136   137       return true;138      }139      catch(Exception e)140      {141       ErrMessage=e.Message; 142       return false;143      }144     }145 }