[gdal-dev] Erdas .img format (HFA) overview troubles

[Frank Warmerdam]

Christiaan Janssen wrote:
> After reading the HFA image format description, I was under the 
> impression that GDAL would support external .ovr files for this 
> format but it seems that is not the case. I ran quick test with gdaladdo 
> ("gdaladdo -ro test.img 2 4 8") and got the following error message: 
> "ERROR 6: BuildOverviews() not supported for this dataset." After poking 
> through the code a bit I can see that HFA driver doesn't seem to be 
> using the default overview manager so it would seem that .ovr files 
> aren't actually ever being used (but i could be wrong). Was this the 
> intended result, or is this a bug?

Christiaan,

I believe this is the intended behavior.  HFA format overviews are always
handling either in the .img file itself, in the .aux file or in an .rrd
file.

If the documentation indicates otherwise, please point out the location and
I'll attempt to clarify it.

Best regards,
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