On 11-09-22 05:00 AM, Jan Hartmann wrote:
Hi, I have a set of unreferenced RGB images with black borders I want to cut off. I do this by adding a fourth alpha band to the image when warping it, and filling this with 255 within the data rectangle, and 0 outside, using gdal_rasterize ( I have the exact georeferenced boundaries of the image as vector data). Nothing happens. When I do the same thing for the first three bands, results are as expected, but whatever I do with the fourth band has no effect at all. Theoretically, this should work, but is there a problem with gdal's implementation of alpha transparency? The following post seems to suggest it: http://osgeo-org.1803224.n2.nabble.com/gdal-dev-Need-help-generating-output-with-alpha-channels-using-Python-API-td6169886.html I didn't try out the suggested solution yet, as I would prefer the simpler method above. Is there really a problem with gdal's handling of alpha transparency, or is there another workaround?
Jan, I don't think the referenced post is related to your problem. If you can bundle up your situation I might be able to investigate tonight. Best regards, -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up | Frank Warmerdam, [email protected] light and sound - activate the windows | http://pobox.com/warmerda and watch the world go round - Rush | Geospatial Software Developer _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
