Generate and Modify Images with GDI+  : Page 4

Creating Thumbnail Images
You can use a similar technique to create a true thumbnail of your image. The Image class supports a GetThumbnailImage method which generates thumbnails. For example:

      const string cstrThumbFileName = 
         "\\Thumb_Sample.gif";
            
      System.Drawing.Image img = 
         System.Drawing.Image.FromFile
      (strFileName);
   
      System.Drawing.Image.GetThumbnailImageAbort 
         imgCallBack = new 
         System.Drawing.Image.GetThumbnailImageAbort
         (CallBackMethod);
   
      System.Drawing.Image imgThumbnail = 
      img.GetThumbnailImage(img.Width/4, 
      img.Height/4, imgCallBack, IntPtr.Zero);
   
      imgThumbnail.Save
         (Application.StartupPath + 
         cstrThumbFileName);

Calling the GetThumbnailImage method and passing in the width and height of the thumbnail, along with an Image.GetThumbnailImageAbort delegate and IntPtr.Zero creates a new instance of the Image object that represents the thumbnail of your original image.

Author Note: The Image.GetThumbnailImageAbort delegate and IntPtr.Zero parameters are required even though they support a callback that is not yet used in GDI+ 1.0.

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