[Gdal-dev] updates of deflate compressed tiff still broken?

[Frank Warmerdam]

On 1/30/06, Vincent Schut <schut at sarvision.nl> wrote:
> Frank et al.,
>
> I'm trying to generate overviews for a compressed (deflate) tiff, which
> doesn't work. I remember updating compressed tiff files being broken,
> either in gdal or in libtiff or both, but has this since never been fixed?

Vincent,

I'm not too sure what is going wrong still with this.   I was able
to reproduce the problems with an averaged overview build on my
test file (http://home.gdal.org/~warmerda/world.tif - converted to
deflate) but without averaging it worked fine.

Also, I found that addtiffo works fine with averaging, so
till this is properly fixed, you might want to just use that.

eg.

addtiffo -r average abc.tif 2 4 8 ...

The code should be very similar between gdaladdo and addtiffo
but apparently there are significant differences.

In the past my assumption has been that these problems related
to issues in the "statefulness" of some of the libtiff codecs, but
I'm not too sure of that anymore.

You can file a bug on this if you wish, but I'm not sure when I'll
get around to digging in deeply.

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