C#生成缩略图的方法

1、需要添加应用System.Drawing.dll

2.命名空间

using System.IO;
using System.Drawing;
using System.Drawing.Imaging;

3、方法一

**//// <summary> 
       /// 生成缩略图 
       /// </summary> 
       /// <param name="originalImagePath">源图路径（物理路径）</param> 
       /// <param name="thumbnailPath">缩略图路径（物理路径）</param> 
       /// <param name="width">缩略图宽度</param> 
       /// <param name="height">缩略图高度</param> 
       /// <param name="mode">生成缩略图的方式</param>     
       public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode) 
       { 
           Image originalImage = Image.FromFile(originalImagePath); 
            
           int towidth = width; 
           int toheight = height; 
        
           int x = 0; 
           int y = 0; 
           int ow = originalImage.Width; 
           int oh = originalImage.Height;         

           switch (mode) 
           {         
               case "HW"://指定高宽缩放（可能变形）                 
                   break; 
               case "W"://指定宽，高按比例                     
                   toheight = originalImage.Height * width/originalImage.Width; 
                   break; 
               case "H"://指定高，宽按比例 
                   towidth = originalImage.Width * height/originalImage.Height;                     
                   break;         
               case "Cut"://指定高宽裁减（不变形）                 
                   if((double)originalImage.Width/(double)originalImage.Height > (double)towidth/(double)toheight) 
                   { 
                       oh = originalImage.Height; 
                       ow = originalImage.Height*towidth/toheight; 
                       y = 0; 
                       x = (originalImage.Width - ow)/2; 
                   } 
                   else 
                   { 
                       ow = originalImage.Width; 
                       oh = originalImage.Width*height/towidth; 
                       x = 0; 
                       y = (originalImage.Height - oh)/2; 
                   } 
                   break;                     
               default : 
                   break; 
           }     
            
           //新建一个bmp图片 
           Image bitmap = new System.Drawing.Bitmap(towidth,toheight); 

           //新建一个画板 
           Graphics g = System.Drawing.Graphics.FromImage(bitmap); 

           //设置高质量插值法 
           g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; 

           //设置高质量,低速度呈现平滑程度 
           g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; 

           //清空画布并以透明背景色填充 
           g.Clear(Color.Transparent);         

           //在指定位置并且按指定大小绘制原图片的指定部分 
           g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight), 
               new Rectangle(x, y, ow,oh), 
               GraphicsUnit.Pixel); 

           try 
           {             
               //以jpg格式保存缩略图 
               bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg); 
           } 
           catch(System.Exception e) 
           { 
               throw e; 
           } 
           finally 
           { 
               originalImage.Dispose(); 
               bitmap.Dispose();                         
               g.Dispose(); 
           } 
       }
View Code

4、方法二

using System.IO;
using System.Drawing;
using System.Drawing.Imaging;

/// <summary>
/// 图片处理类
/// 1、生成缩略图片或按照比例改变图片的大小和画质
/// 2、将生成的缩略图放到指定的目录下
/// </summary>
public class ImageClass
{
    public Image ResourceImage;
    private int ImageWidth;
    private int ImageHeight;

    public string ErrMessage;

    /// <summary>
    /// 类的构造函数
    /// </summary>
    /// <param name="ImageFileName">图片文件的全路径名称</param>

    public ImageClass(string ImageFileName)
    {
        ResourceImage=Image.FromFile(ImageFileName);
     ErrMessage="";
    }

    public bool ThumbnailCallback()
    {
     return false;
    }

    /// <summary>
    /// 生成缩略图重载方法1，返回缩略图的Image对象
    /// </summary>
    /// <param name="Width">缩略图的宽度</param>
    /// <param name="Height">缩略图的高度</param>
    /// <returns>缩略图的Image对象</returns>
    public Image GetReducedImage(int Width,int Height)
    {
     try
     {
      Image ReducedImage;

      Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback); 
     
      ReducedImage=ResourceImage.GetThumbnailImage(Width,Height,callb,IntPtr.Zero);
  
      return ReducedImage;
     }
     catch(Exception e)
     {
      ErrMessage=e.Message; 
         return null;
     }
    }

    /// <summary>
    /// 生成缩略图重载方法2，将缩略图文件保存到指定的路径
    /// </summary>
    /// <param name="Width">缩略图的宽度</param>
    /// <param name="Height">缩略图的高度</param>
    /// <param name="targetFilePath">缩略图保存的全文件名，(带路径)，参数格式：D:Imagesfilename.jpg</param>
    /// <returns>成功返回true，否则返回false</returns>
    public bool GetReducedImage(int Width,int Height,string targetFilePath)
    {
     try
     {
      Image ReducedImage;

      Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback); 
     
      ReducedImage=ResourceImage.GetThumbnailImage(Width,Height,callb,IntPtr.Zero);
      ReducedImage.Save(@targetFilePath,ImageFormat.Jpeg);

      ReducedImage.Dispose(); 
  
      return true;
     }
     catch(Exception e)
     {
      ErrMessage=e.Message; 
      return false;
     }
    }

    /// <summary>
    /// 生成缩略图重载方法3，返回缩略图的Image对象
    /// </summary>
    /// <param name="Percent">缩略图的宽度百分比 如：需要百分之80，就填0.8</param>  
    /// <returns>缩略图的Image对象</returns>
    public Image GetReducedImage(double Percent)
    {
     try
     {
      Image ReducedImage;

      Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback);

      ImageWidth=Convert.ToInt32(ResourceImage.Width*Percent);
      ImageHeight=Convert.ToInt32(ResourceImage.Width*Percent);
     
      ReducedImage=ResourceImage.GetThumbnailImage(ImageWidth,ImageHeight,callb,IntPtr.Zero);
  
      return ReducedImage;
     }
     catch(Exception e)
     {
      ErrMessage=e.Message; 
      return null;
     }
    }

    /// <summary>
    /// 生成缩略图重载方法4，返回缩略图的Image对象
    /// </summary>
    /// <param name="Percent">缩略图的宽度百分比 如：需要百分之80，就填0.8</param>  
    /// <param name="targetFilePath">缩略图保存的全文件名，(带路径)，参数格式：D:Imagesfilename.jpg</param>
    /// <returns>成功返回true,否则返回false</returns>
    public bool GetReducedImage(double Percent,string targetFilePath)
    {
     try
     {
      Image ReducedImage;

      Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback);

      ImageWidth=Convert.ToInt32(ResourceImage.Width*Percent);
      ImageHeight=Convert.ToInt32(ResourceImage.Width*Percent);
     
      ReducedImage=ResourceImage.GetThumbnailImage(ImageWidth,ImageHeight,callb,IntPtr.Zero);

      ReducedImage.Save(@targetFilePath,ImageFormat.Jpeg);

      ReducedImage.Dispose(); 
  
      return true;
     }
     catch(Exception e)
     {
      ErrMessage=e.Message; 
      return false;
     }
    }


}
View Code

5、亲测可用

  1 using System;
  2 using System.Collections.Generic;
  3 using System.Linq;
  4 using System.Text;
  5 using System.IO;
  6 using System.Drawing;
  7 using System.Drawing.Imaging;
  8 
  9 namespace ConsoleApplication2
 10 {
 11     class Program
 12     {
 13         static void Main(string[] args)
 14         {
 15             string originalImagePath ="D:/pic/2012cnu-gisBarbecue/IMG_7226.JPG";
 16             string thumbnailPath ="D:/pic/2012cnu-gisBarbecue/14.jpg";
 17             MakeThumbnail(originalImagePath, thumbnailPath, 200, 200, "W");
 18             thumbnailPath = "D:/pic/2012cnu-gisBarbecue/15.jpg";
 19             ImageClass imageC = new ImageClass(originalImagePath);
 20             imageC.GetReducedImage(0.5, thumbnailPath);
 21         }
 22         /**/
 23         /// <summary> 
 24         /// 生成缩略图 
 25         /// </summary> 
 26         /// <param name="originalImagePath">源图路径（物理路径）</param> 
 27         /// <param name="thumbnailPath">缩略图路径（物理路径）</param> 
 28         /// <param name="width">缩略图宽度</param> 
 29         /// <param name="height">缩略图高度</param> 
 30         /// <param name="mode">生成缩略图的方式</param>     
 31         public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
 32         {
 33             Image originalImage = Image.FromFile(originalImagePath);
 34 
 35             int towidth = width;
 36             int toheight = height;
 37 
 38             int x = 0;
 39             int y = 0;
 40             int ow = originalImage.Width;
 41             int oh = originalImage.Height;
 42 
 43             switch (mode)
 44             {
 45                 case "HW"://指定高宽缩放（可能变形）                 
 46                     break;
 47                 case "W"://指定宽，高按比例                     
 48                     toheight = originalImage.Height * width / originalImage.Width;
 49                     break;
 50                 case "H"://指定高，宽按比例 
 51                     towidth = originalImage.Width * height / originalImage.Height;
 52                     break;
 53                 case "Cut"://指定高宽裁减（不变形）                 
 54                     if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
 55                     {
 56                         oh = originalImage.Height;
 57                         ow = originalImage.Height * towidth / toheight;
 58                         y = 0;
 59                         x = (originalImage.Width - ow) / 2;
 60                     }
 61                     else
 62                     {
 63                         ow = originalImage.Width;
 64                         oh = originalImage.Width * height / towidth;
 65                         x = 0;
 66                         y = (originalImage.Height - oh) / 2;
 67                     }
 68                     break;
 69                 default:
 70                     break;
 71             }
 72 
 73             //新建一个bmp图片 
 74             Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
 75 
 76             //新建一个画板 
 77             Graphics g = System.Drawing.Graphics.FromImage(bitmap);
 78 
 79             //设置高质量插值法 
 80             g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
 81 
 82             //设置高质量,低速度呈现平滑程度 
 83             g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
 84 
 85             //清空画布并以透明背景色填充 
 86             g.Clear(Color.Transparent);
 87 
 88             //在指定位置并且按指定大小绘制原图片的指定部分 
 89             g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight),
 90                 new Rectangle(x, y, ow, oh),
 91                 GraphicsUnit.Pixel);
 92 
 93             try
 94             {
 95                 //以jpg格式保存缩略图 
 96                 bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
 97             }
 98             catch (System.Exception e)
 99             {
100                 throw e;
101             }
102             finally
103             {
104                 originalImage.Dispose();
105                 bitmap.Dispose();
106                 g.Dispose();
107             }
108         }
109     }
110     public class ImageClass
111     {
112         public Image ResourceImage;
113         private int ImageWidth;
114         private int ImageHeight;
115 
116         public string ErrMessage;
117 
118         /// <summary>
119         /// 类的构造函数
120         /// </summary>
121         /// <param name="ImageFileName">图片文件的全路径名称</param>
122         public ImageClass(string ImageFileName)
123         {
124             ResourceImage = Image.FromFile(ImageFileName);
125             ErrMessage = "";
126         }
127 
128         public bool ThumbnailCallback()
129         {
130             return false;
131         }
132 
133         /// <summary>
134         /// 生成缩略图重载方法1，返回缩略图的Image对象
135         /// </summary>
136         /// <param name="Width">缩略图的宽度</param>
137         /// <param name="Height">缩略图的高度</param>
138         /// <returns>缩略图的Image对象</returns>
139         public Image GetReducedImage(int Width, int Height)
140         {
141             try
142             {
143                 Image ReducedImage;
144 
145                 Image.GetThumbnailImageAbort callb = new Image.GetThumbnailImageAbort(ThumbnailCallback);
146 
147                 ReducedImage = ResourceImage.GetThumbnailImage(Width, Height, callb, IntPtr.Zero);
148 
149                 return ReducedImage;
150             }
151             catch (Exception e)
152             {
153                 ErrMessage = e.Message;
154                 return null;
155             }
156         }
157 
158         /// <summary>
159         /// 生成缩略图重载方法2，将缩略图文件保存到指定的路径
160         /// </summary>
161         /// <param name="Width">缩略图的宽度</param>
162         /// <param name="Height">缩略图的高度</param>
163         /// <param name="targetFilePath">缩略图保存的全文件名，(带路径)，参数格式：D:Imagesfilename.jpg</param>
164         /// <returns>成功返回true，否则返回false</returns>
165         public bool GetReducedImage(int Width, int Height, string targetFilePath)
166         {
167             try
168             {
169                 Image ReducedImage;
170 
171                 Image.GetThumbnailImageAbort callb = new Image.GetThumbnailImageAbort(ThumbnailCallback);
172 
173                 ReducedImage = ResourceImage.GetThumbnailImage(Width, Height, callb, IntPtr.Zero);
174                 ReducedImage.Save(@targetFilePath, ImageFormat.Jpeg);
175 
176                 ReducedImage.Dispose();
177 
178                 return true;
179             }
180             catch (Exception e)
181             {
182                 ErrMessage = e.Message;
183                 return false;
184             }
185         }
186 
187         /// <summary>
188         /// 生成缩略图重载方法3，返回缩略图的Image对象
189         /// </summary>
190         /// <param name="Percent">缩略图的宽度百分比 如：需要百分之80，就填0.8</param>  
191         /// <returns>缩略图的Image对象</returns>
192         public Image GetReducedImage(double Percent)
193         {
194             try
195             {
196                 Image ReducedImage;
197 
198                 Image.GetThumbnailImageAbort callb = new Image.GetThumbnailImageAbort(ThumbnailCallback);
199 
200                 ImageWidth = Convert.ToInt32(ResourceImage.Width * Percent);
201                 ImageHeight = Convert.ToInt32(ResourceImage.Width * Percent);
202 
203                 ReducedImage = ResourceImage.GetThumbnailImage(ImageWidth, ImageHeight, callb, IntPtr.Zero);
204 
205                 return ReducedImage;
206             }
207             catch (Exception e)
208             {
209                 ErrMessage = e.Message;
210                 return null;
211             }
212         }
213 
214         /// <summary>
215         /// 生成缩略图重载方法4，返回缩略图的Image对象
216         /// </summary>
217         /// <param name="Percent">缩略图的宽度百分比 如：需要百分之80，就填0.8</param>  
218         /// <param name="targetFilePath">缩略图保存的全文件名，(带路径)，参数格式：D:Imagesfilename.jpg</param>
219         /// <returns>成功返回true,否则返回false</returns>
220         public bool GetReducedImage(double Percent, string targetFilePath)
221         {
222             try
223             {
224                 Image ReducedImage;
225 
226                 Image.GetThumbnailImageAbort callb = new Image.GetThumbnailImageAbort(ThumbnailCallback);
227 
228                 ImageWidth = Convert.ToInt32(ResourceImage.Width * Percent);
229                 ImageHeight = Convert.ToInt32(ResourceImage.Width * Percent);
230 
231                 ReducedImage = ResourceImage.GetThumbnailImage(ImageWidth, ImageHeight, callb, IntPtr.Zero);
232 
233                 ReducedImage.Save(@targetFilePath, ImageFormat.Jpeg);
234 
235                 ReducedImage.Dispose();
236 
237                 return true;
238             }
239             catch (Exception e)
240             {
241                 ErrMessage = e.Message;
242                 return false;
243             }
244         }
245 
246 
247     }
248 
249 }
View Code
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原文地址：https://www.cnblogs.com/lwngreat/p/4857677.html