final public function imagePNG($filename = null, $quality = -1, $filters = PNG_NO_FILTER)
	{
		return imagepng($this->_image_handle, $filename, $quality, $filters);
	}
final public function imagePNG($filename = null, $quality = -1, $filters = PNG_NO_FILTER)
	{
		return imagepng($this->_image_handle, $filename, $quality, $filters);
	}
final public function imagePNG ( $ filename = null , $ quality = - 1 , $ filters = PNG_NO_FILTER ) { return imagepng ( $ this -> _image_handle , $ filename , $ quality , $ filters ) ; }
Output a PNG image to either the browser or a file

@param string  $filename The path to save the file to. null outputs directly
@param int     $quality  Compression level: from 0 (no compression) to 9.
@param int     $filters  Any combination of the PNG_FILTER_XXX constants.
@return bool             True on success, false on failure
Output a PNG image to either the browser or a file