Returns the specified code-block in the current tile for the specified component, as a copy (see below).

       <p>The returned code-block may be progressive, which is indicated by
       the 'progressive' variable of the returned 'DataBlk' object. If a
       code-block is progressive it means that in a later request to this
       method for the same code-block it is possible to retrieve data which is
       a better approximation, since meanwhile more data to decode for the
       code-block could have been received. If the code-block is not
       progressive then later calls to this method for the same code-block
       will return the exact same data values.</p><p>The data returned by this method is always a copy of the internal
       data of this object, if any, and it can be modified "in place" without
       any problems after being returned. The 'offset' of the returned data is 
       0, and the 'scanw' is the same as the code-block width. See the
       'DataBlk' class.</p>