[gdal-dev] Transparency mask (alpha band) in ECW

Jukka Rahkonen jukka.rahkonen at maanmittauslaitos.fi
Wed Jul 8 03:46:27 PDT 2015


Nodata values with lossy compression like JPEG, ECW, or JPEG2000 do not
really work. I noticed that newest ECW SDK versions (>= 4) have support for
using a transparency mask:


"Using the ECWJP2 SDK terminology, a transparency mask is implemented as an
opacity band called AllOpacity."

GDAL ECW driver does not have support for this. I wonder if it could be
doable and if I should make a feature request. I also wonder if GDAL can
decode ECW files which have transparency mask correctly.

-Jukka Rahkonen-

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