[gdal-dev] Applying colour/contrast corrections to geotiffs

Paul Norman penorman at mac.com
Mon Mar 11 14:42:01 PDT 2013

> From: Even Rouault [mailto:even.rouault at mines-paris.org]
> Sent: Monday, March 11, 2013 1:55 PM
> Subject: Re: [gdal-dev] Applying colour/contrast corrections to geotiffs
> > If you run nearblack to go from one JPEG in TIFF to another JPEG in
> > TIFF, does it use this optimization for the RGB bands?
> I don't see the interest of doing nearblack from JPEG-in-TIFF to JPEG-
> in-TIFF.
> Nearblack can be interesting from JPEG-in-TIFF to lossless-TIFF to
> eliminate near zero values at the edge of the imagery due to JPEG
> compression. But once you get again to JPEG-in-TIFF, the artifacts will
> come again.

The issue I have the imagery has an irregular edge and the result of the WMS
server when transparency is off has either black boundaries for the very
outside or white ones for parts inside of that. It also has pixels within
the image which are 100% white where there was lens flare or snow on the
ground, so only the edge white areas are no data areas. nearblack is the
only software I'm aware of which deals with areas of a solid colour around a

I haven't given much thought to how process it after the download stage yet.
I will have some time to think about this because the download stage will
take so long. My first step is to download an area I can test with. I'd
welcome suggestions!

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