Le mercredi 08 juillet 2015 12:46:27, Jukka Rahkonen a écrit : > 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, 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 Driver: ECW/ERDAS Compressed Wavelets (SDK 5.0) Files: ../gdrivers/data/stefan_full_rgba_ecwv3_meta.ecw Size is 162, 150 Coordinate System is `' Metadata: CLOCKWISE_ROTATION_DEG=0.000000 COLORSPACE=RGB COMPRESSION_DATE=2013-04-04T09:20:03Z COMPRESSION_RATE_ACTUAL=3.165093 COMPRESSION_RATE_TARGET=20 FILE_METADATA_ACQUISITION_DATE=2012-09-12 FILE_METADATA_ACQUISITION_SENSOR_NAME=Leica ADS-80 FILE_METADATA_ADDRESS=2 Abbotsford Street, West Leederville WA 6007 Australia FILE_METADATA_AUTHOR=Unknown FILE_METADATA_CLASSIFICATION=test gdal image FILE_METADATA_COMPANY=ERDAS-QA FILE_METADATA_COMPRESSION_SOFTWARE=python2.7/GDAL v1.10.0.0/ECWJP2 SDK v5.0.0.0 FILE_METADATA_COPYRIGHT=Intergraph 2013 [email protected] FILE_METADATA_TELEPHONE=+61 8 9388 2900 VERSION=3 Corner Coordinates: Upper Left ( 0.0, 0.0) Lower Left ( 0.0, 150.0) Upper Right ( 162.0, 0.0) Lower Right ( 162.0, 150.0) Center ( 81.0, 75.0) Band 1 Block=256x256 Type=Byte, ColorInterp=Red Description = Red Overviews: arbitrary Mask Flags: PER_DATASET ALPHA Band 2 Block=256x256 Type=Byte, ColorInterp=Green Description = Green Overviews: arbitrary Mask Flags: PER_DATASET ALPHA Band 3 Block=256x256 Type=Byte, ColorInterp=Blue Description = Blue Overviews: arbitrary Mask Flags: PER_DATASET ALPHA Band 4 Block=256x256 Type=Byte, ColorInterp=Alpha Description = AllOpacity Overviews: arbitrary 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) Even -- Spatialys - Geospatial professional services http://www.spatialys.com _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
