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

[Jukka Rahkonen]

Hi,

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:

http://blog.hexagongeospatial.com/help-ecw-speckled-edges/

"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-