For those not wanting or needing to take the processing hit of running
nearblack, use gdalwarp and -dstalpha to create the alpha channel, and use
intermediate VRT to save space and more time. Something like this:
gdalwarp -srcnodata 0 -dstalpha -of vrt source.tif xx-interim.vrt
gdal_translate -of COG {...} xx-interim.vrt final.tif
-Matt
From: gdal-dev <gdal-dev-boun...@lists.osgeo.org> On Behalf Of Travis Kirstine
Sent: July 22, 2022 9:04 AM
To: gdal dev <gdal-dev@lists.osgeo.org>
Subject: Re: [gdal-dev] JPEG compressed COGs nodata
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To answer my own question I believe the answer is that you need to create an
alpha band when working with RGB datasets to have JPEG compressed COGs without
compression artifacts in the nodata areas. Creating a internal mask on the
source data may work as well but I haven't tried.
# add a alpha band using the nearblack utility
nearblack -setalpha rgb_nodata.tif -o rgba.tif
# create the COG
gdal_translate -of COG -co COMPRESS=JPEG -co
TILING_SCHEME=GoogleMapsCompatible -co NUM_THREADS=ALL_CPUS -co BIGTIFF=YES
rgba.tif cog.tif
Regards
On Tue, 19 Jul 2022 at 15:19, Travis Kirstine
<traviskirst...@gmail.com<mailto:traviskirst...@gmail.com>> wrote:
I've been trying to create a COG with JPEG compression with transparent nodata
values without much success. Is this possible without creating a secondary
mask?
Any hints?
Regards
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