Hi List, I was checking a gdalwarp (GDAL 2.1.2) invokation with a colleague and I have a question.
I know that when warping a geotiff with internal NODATA_VALUES=0 0 0 metadata, only RGB pixels = 0 0 0 are handled as nodata whilst pixels like "0 2 4", "50 0 0" will not right? In the past, I had issues using -scrnodata 0 instead of embedded NODATA_VALUES=0 0 0, getting results with sparse nodata around due to band_i = 0 being interpreted as a nodata pixels. This is why I usually suggest to define the NODATA_VALUES metadata to make sure only the exact triplet is handled as nodata. However, today we have processed a simple UTM RGB dataset (without NODATA_VALUES metadata defined) using this command: gdalwarp -t_srs EPSG:4326 -srcnodata 0 -dstnodata None -dstalpha And the result is properly rendered: the alpha mask is zero only where the input pixels are "0 0 0" which is exactly what we needed. Do something has been changed in the latest versions? Is the alpha band mask being set to zero only when all input pixels are zero? Thanks for the clarification. Cheers, Daniele -- == GeoServer Professional Services from the experts! Visit http://goo.gl/it488V for more information. == Ing. Daniele Romagnoli Senior Software Engineer GeoSolutions S.A.S. Via di Montramito 3/A 55054 Massarosa (LU) Italy phone: +39 0584 962313 fax: +39 0584 1660272 http://www.geo-solutions.it http://twitter.com/geosolutions_it ------------------------------------------------------- *AVVERTENZE AI SENSI DEL D.Lgs. 196/2003* Le informazioni contenute in questo messaggio di posta elettronica e/o nel/i file/s allegato/i sono da considerarsi strettamente riservate. Il loro utilizzo è consentito esclusivamente al destinatario del messaggio, per le finalità indicate nel messaggio stesso. Qualora riceviate questo messaggio senza esserne il destinatario, Vi preghiamo cortesemente di darcene notizia via e-mail e di procedere alla distruzione del messaggio stesso, cancellandolo dal Vostro sistema. Conservare il messaggio stesso, divulgarlo anche in parte, distribuirlo ad altri soggetti, copiarlo, od utilizzarlo per finalità diverse, costituisce comportamento contrario ai principi dettati dal D.Lgs. 196/2003. The information in this message and/or attachments, is intended solely for the attention and use of the named addressee(s) and may be confidential or proprietary in nature or covered by the provisions of privacy act (Legislative Decree June, 30 2003, no.196 - Italy's New Data Protection Code).Any use not in accord with its purpose, any disclosure, reproduction, copying, distribution, or either dissemination, either whole or partial, is strictly forbidden except previous formal approval of the named addressee(s). If you are not the intended recipient, please contact immediately the sender by telephone, fax or e-mail and delete the information in this message that has been received in error. The sender does not give any warranty or accept liability as the content, accuracy or completeness of sent messages and accepts no responsibility for changes made after they were sent or for other risks which arise as a result of e-mail transmission, viruses, etc.
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