[Gdal-dev] Imagine overviews option

[Frank Warmerdam]

On 9/16/05, Garrett Potts <potts at cfl.rr.com> wrote:
> Hello Frank/All:
> 
> I was told that you have added imagine overview building both
> creating internal overview and for creating a .rrd file.  I didn't
> see an option string added that could specify either method.  What is
> the generic interface to create either option for imagine output files.

Garrett, 

By default now gdaladdo on .img file will create Imagine style
overviews instead of a GDAL .ovr file (TIFF).  By default they are
created in the .img file unless they will be too big in which case
a spill file (.ige) is created.

If you set the HFA_USE_RRD configuration option to YES then 
an external .rrd file will be used for the overviews instead of 
putting them right in the .img file.  Unfortunately, I did not include
an "options list" in the BuildOverviews() methods in GDAL so there
is no way to pass options like this into the overview building method.
And options passed to the original file creation are not preserved 
to the point that overviews are build (which is not part of file creation). 

Config values can be set as environment variables, on the command
line with the --config switch, or in C using the CPLSetConfigOption()
function. 

eg. 

setenv HFA_USE_RRD=YES

or

gdaladdo --config HFA_USE_RRD YES abc.img

or

CPLSetConfigOption( "HFA_USE_RRD", "YES" );
...

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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