[gdal-dev] update to overview resampling methods?

[Even Rouault]

> >> 
> >> 1) why are some methods not listed in GDALDataset::BuildOverviews and
> >> gdaladdo docs
> >> average_mp, AVERAGE_BIT2*, NO_REGEN  (there may be others)
> > 
> > - average_mp is documented in gdaladdo as not ready for use in
> > production, so could be likely "undocumented" in gdaladdo man page
> > - AVERAGE_BIT2* stuff is internal implementation detail for computing
> > overviews of 1-bit raster as a 8-bit band. Must not be documented in
> > user doc.
> > - NO_REGEN: implementation hack for Imagine overviews. Must
> > not be documented in user doc
> 
> I understand that these are set internally when a certain condition is met?

Actually, about AVERAGE_BIT2GRAYSCALE, I was a bit quick in my answer. It is a 
value that can be passed to BuildOverviews(). This has been implemented per 
http://trac.osgeo.org/gdal/ticket/1908 . Seems that the documentation part was 
never done.

For NO_REGEN, if you're really curious about it, you'll have to study the HFA 
driver. (But only if you are bored and have nothing more interesting to do 
;-))

> >> 3) why is AVERAGE_MP considered unfit for use in the gdaladdo docs?
> >> and why is it still available?
> > 
> > Historical remain ? Could likely be undocumented.
> 
> ok I will remove it, should it be removed/commented from the code also?

Undocumenting seems appropriate. As far as removing the implementation, you 
might want to check with the original committer (FrankW)