[Gdal-dev] RFC 15: Band Masks

[Frank Warmerdam]

Folks,

After some thinking, and discussions with Howard, I have revised RFC 15
a bunch.  Highlights:

  o Now I plan to return alpha bands as the mask if they apply.
  o I have changed the name of the methods to just GetMaskBand() and
    get GetMaskFlags() to avoid confusion.
  o I have written in more detail about the default implementation.
  o I have changed the GetMaskType() to GetMaskFlags() with flags bitwise
    or'ed together for expandability and so multiple conditions can apply at
    once.

I have also explicitly indicated that the API is not being extended at this
time for the creation of masks.  Driver CreateCopy() implementations can
capture masks from the source dataset if applicable, but that is the only
mechanism GDAL can use to create them for now.  Related to this, I'm
avoiding addressing band masks in PAM (the persistant auxilary metadata
mechanism).  I'm doing this mostly to keep things managable for now, and
because I think some careful thinking needs to be applied before trying
to provide explicit creation.

   http://trac.osgeo.org/gdal/wiki/rfc15_nodatabitmask

I'm very pleased with the move to expressing nodata, alpha bands and
explicit bitmasks all through the mask model.  I hope others will feel
the same!

Best regards,
-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org