I have added a ticked for such an issue long ago, but I don't remember what would be the expected solution. http://trac.osgeo.org/gdal/ticket/2279
There should be an external config option to instruct the driver which representation should be used. Best regards, Tamas 2012/5/29 Craig Bruce <[email protected]>: > I have run into a problem using GDAL to read TIFF images with a alpha > channels. GDAL returns the source TIFF sample values verbatim regardless > of whether the alpha channel is associated (pre-multiplied) or unassociated > within the TIFF image samples. (In each alpha model, the same pixel > value with the same alpha value will have different sample values.) > > GDAL does not appear to enforce a specific alpha model in its interface > (pre-multiplied or non-pre-multiplied) and does not appear to offer any > indication of which is currently being used. This creates a dead end as > far as the GDAL interface goes. My system and most image formats (e.g., > PNG) use the non-pre-multiplied alpha model. TIFF can use either. > > What is a user supposed to do about this? > > --------------------------+----------------------+-------------------------- > Dr. Craig S. Bruce | Ph 819-771-8303 x205 | CubeWerx Inc. > Senior Software Developer | Fax 819-771-8388 | Gatineau, Québec, Canada > [email protected] | http://csbruce.com/ | http://www.cubewerx.com/ > --------------------------+----------------------+-------------------------- > "How many legs does a dog have if you call the tail a leg? Four. > Calling a tail a leg doesn't make it a leg." -- Abraham Lincoln > _______________________________________________ > 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
