Description
bool 
imagegd2 ( resource image [, string filename [, int chunk_size [, int type]]] )
     imagegd2() outputs a GD2 image to
     filename.
     The image parameter is the return from the
     imagecreatetruecolor() function.
    
     The filename parameter is optional, and if left
     off, the raw image stream will be output directly.
    
     The optional type parameter is either 
     IMG_GD2_RAW or IMG_GD2_COMPRESSED.
     Default is IMG_GD2_RAW.
    
Note: 
      The optional chunk_size and
      type parameters became available
      in PHP 4.3.2.
     
Note: 
      The GD2 format is commonly used to allow fast loading of parts of images.
      Note that the GD2 format is only usable in GD2-compatible applications.
     
Note: This function requires GD 2.0.1 or later.
     See also imagegd()