[Gdal-dev] gdaladdo with .rrd ignoring compress overviews?

[Matt Wilkie]

> Erdas Imagine files don't support LZW.  RLC is the only supported 
> compression (I think).

Thanks for clearing that up. I did some tests and it appears that 
"gdal_translate -of hfa -co compress=anydarntextyouwant" always results 
in RLC compression. This includes "compress=none", though "compress=no" 
does yield no compression. I can't think of a use case for not 
compressing though.


> Frankly, I don't know why it even used the RLC compression.  I don't
> see any support for the COMPRESS_OVERVIEW config option in the
> HFA/.img/.aux code.

I was going to submit changes to the docs to help others following my
same train of thoughts, but now I'm more confused. From
http://www.gdal.org/gdaladdo.html:

    Create an external compressed GeoTIFF overview file
    from the ERDAS .IMG file:
    gdaladdo --config COMPRESS_OVERVIEW DEFLATE erdas.img 2 4 8 16

But for me this creates embedded overviews.
The next example from the same page yields an error:

    > gdaladdo --config USE_RRD YES overtest3.jpg 3 9 27 81
    ERROR 6: The JPEG driver does not support update access to
    existing datasets.

    0...11...20...31...40...51...60...71...80...91...100 - done.
    0...11...20...31...40...51...60...71...80...91...100 - done.
    0...11...20...31...40...51...60...71...80...91...100 - done.

cheers,

-- 
matt wilkie
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