Jukka, Even, Here is an example of ECW v2 with opacity. https://trac.osgeo.org/gdal/ticket/6028
Regards. Jacek Tomaka -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Even Rouault Sent: Wednesday, 8 July 2015 8:08 PM To: [email protected] Cc: Jukka Rahkonen Subject: Re: [gdal-dev] Transparency mask (alpha band) in ECW Le mercredi 08 juillet 2015 14:01:47, Jukka Rahkonen a écrit : > Even Rouault <even.rouault <at> spatialys.com> writes: > > > 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, > > > > I'm a bit confused by the above. If you look to the bottom of the > > page you mentio,n you'll see a gdalinfo report with an alpha band. > > > > And I've just tried with a test file of the autotest suite: > > > > gdalinfo ../gdrivers/data/stefan_full_rgba_ecwv3_meta.ecw > > .... > > > This is a ECWv3 file. I don't have an example with ECWv2 and the > > "appended" mask, but I believe the driver should also likely be able > > to read/write this (but I haven't a ECWv2 image with alpha handy) > > Hi Even, > > I apologize, No problem > I do not use ECW myself nowadays but I was reading this > gis.stackexchange question which deals actually with FME > http://gis.stackexchange.com/questions/153490/how-to-convert-tif-to-ec > w-wit > h-fme-maintaining-a-certain-value?noredirect=1#comment225797_153490 > > Then I read our ECW manual page http://www.gdal.org/frmt_ecw.html > which does not talk anything about nodata, alpha, transparency etc. I > just thought that we can't handle nodata any better than FME but > obviously we can. I do not have SDK license so I could not test ECW output > myself. > > Is the ECW transparency band created automatically if user has > Read/Write SDK >= 4.0 and source data has either alpha channel or > nodata set in GeoTIFF? As far as I understand the code, yes that should be automatic if the 4th band of the source raster is advertized as an Alpha channel. > ECW driver does not seem to have any creation option for that but > perhaps it is not necessary. > > -Jukka- > > > _______________________________________________ > gdal-dev mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/gdal-dev -- Spatialys - Geospatial professional services http://www.spatialys.com _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
