. NET

. NET method for generating thumbnails 1. Use the GetThumbnailImage method of the Image to directly generate a compressed Image. This is probably the case:

File: // set the EncoderParameters object of the original image object and set the definition.

 
 

  
  
ImageCodecInfo ici = GetCodecInfo((string)htmimes[mFileExtName]);     
  
  
   EncoderParameters parameters = new EncoderParameters(1);     
  
  
   parameters.Param[0] = new EncoderParameter(Encoder.Quality,lngDefinition);     
  
  
    
  
  
   System.Drawing.Image.GetThumbnailImageAbort myCallback =new      
  
  
    
  
  
   System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback);     
  
  
   System.Drawing.Image myThumbnail = image.GetThumbnailImage(intNewWidth, intNewHeight,      
  
  
    
  
  
 myCallback, IntPtr.Zero);     
  
  
  myThumbnail.Save(txtNewPath, ici, parameters);    
  
  
ImageCodecInfo ici = GetCodecInfo((string)htmimes[mFileExtName]);  
  
  
   EncoderParameters parameters = new EncoderParameters(1);  
  
  
   parameters.Param[0] = new EncoderParameter(Encoder.Quality,lngDefinition);  
  
  
 
  
  
   System.Drawing.Image.GetThumbnailImageAbort myCallback =new   
  
  
 
  
  
   System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback);  
  
  
   System.Drawing.Image myThumbnail = image.GetThumbnailImage(intNewWidth, intNewHeight,   
  
  
 
  
  
 myCallback, IntPtr.Zero);  
  
  
  myThumbnail.Save(txtNewPath, ici, parameters);  
  
  
   
 
 

. NET method for generating thumbnails 2. Use Graphics to re-draw images

 
 

  
  
ImageCodecInfo ici = GetCodecInfo ((String) Htmimes [mFileExtName]);
  
  
EncoderParameters parameters =NewEncoderParameters (1 );
  
  
Parameters. Param [0] =NewEncoderParameter (Encoder. Quality, lngDefinition );
  
  

  
  
Bitmap objNewBitMap =NewBitmap (intNewWidth, intNewHeight, PixelFormat. Format32bppArgb );
  
  
// Create a new Graphics object from the specified Image object 
  
  
Graphics objGraphics = Graphics. FromImage (objNewBitMap );
  
  
// Clear the entire drawing surface and fill it with a transparent background color 
  
  
ObjGraphics. Clear (Color. Transparent );
  
  
// Draw the original image object at the specified position and by the specified size 
  
  
ObjGraphics. DrawImage (image,NewRectangle (0, 0, intNewWidth, intNewHeight ));
  
  
ObjNewBitMap. Save (txtNewPath + txtNewFileName +"."+ MFileExtName, ici, parameters );
  
  
ImageCodecInfo ici = GetCodecInfo ((String) Htmimes [mFileExtName]);
  
  
EncoderParameters parameters =NewEncoderParameters (1 );
  
  
Parameters. Param [0] =NewEncoderParameter (Encoder. Quality, lngDefinition );
  
  
 
  
  
Bitmap objNewBitMap =NewBitmap (intNewWidth, intNewHeight, PixelFormat. Format32bppArgb );
  
  
// Create a new Graphics object from the specified Image object 
  
  
Graphics objGraphics = Graphics. FromImage (objNewBitMap );
  
  
// Clear the entire drawing surface and fill it with a transparent background color 
  
  
ObjGraphics. Clear (Color. Transparent );
  
  
// Draw the original image object at the specified position and by the specified size 
  
  
ObjGraphics. DrawImage (image,NewRectangle (0, 0, intNewWidth, intNewHeight ));
  
  
ObjNewBitMap. Save (txtNewPath + txtNewFileName +"."+ MFileExtName, ici, parameters );
  
  
 
 
 

Note that lngDefinition is a LONG parameter to adjust the definition. Generally, it is clear from 50 to 90.

. NET generates two kinds of thumbnail effects. Graphics is better in definition (with the same width and height), and Graphics is smaller in rendering, which is about 1/3 smaller.

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