<div dir="ltr">Hi Daniele,<div><br></div><div>Even added this functionality to VRTs just recently, see</div><div><br></div><div><a href="https://lists.osgeo.org/pipermail/gdal-dev/2020-December/053178.html">https://lists.osgeo.org/pipermail/gdal-dev/2020-December/053178.html</a><br></div><div><br></div><div>I think it is slated for GDAL 3.3 but you could always build the bleeding edge.</div><div><br></div><div>Patrick</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Jan 27, 2021 at 3:50 AM Daniele Romagnoli <<a href="mailto:daniele.romagnoli@geo-solutions.it">daniele.romagnoli@geo-solutions.it</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">Hi list,<div>I have some TIFF datasets with partially overlapping edges and embedded binary masks to keep into account which parts along the edges should be masked out.</div><div>When showing all the images on QGIS it looks good since the binary mask do its job by making the "black/white" overlapping edge masked out.</div><div><br></div><div>Now I need to create a single TIF from all of these images.</div><div>I have tried with gdalbuildvrt but it doesn't produce good result.</div><div>Checking the doc I saw this:</div><div><br></div><div><i><span style="color:rgb(64,64,64);font-family:Lato,proxima-nova,"Helvetica Neue",Arial,sans-serif;background-color:rgb(252,252,252)">If there is some amount of spatial overlapping between files [...] currently, alpha channel is not taken into account to do alpha compositing (so a source with alpha=0 appearing on top of another source will override is content). This might be changed in later versions.</span> <br></i></div><div><i><br></i></div><div>So I think it's expected and I have switched to gdal_merge.py.</div><div>It works better since it does alpha compositing but it looks like the result doesn't preserve the binary mask which I still need since I have M groups of N files which I need to process in 2 passes:</div><div>- the inner group of N files get merged using the binary mask to a bigger file.</div><div>- all the M bigger files get mosaicked again to a single huge file.</div><div><br></div><div>I will spend some more time in testing different attempts.</div><div>In the meantime, do you have any suggestion or past experience on how to deal with that?</div><div>Side note: I have vague memory of gdal_merge being somehow memory bounded, throwing memory allocation errors when trying to compose big images. This is why in the past I was using gdalbuildvrt to do composition (without overlapping).</div><div><br></div><div>Thanks in advance.</div><div>Regards,</div><div>Daniele</div><div><br></div><div><br></div><div> <br clear="all"><div><br></div>-- <br><div dir="ltr"><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr">Regards,</div><div dir="ltr">Daniele Romagnoli</div><div dir="ltr">==</div><div dir="ltr">GeoServer Professional Services from the experts! Visit <a href="http://goo.gl/it488V" target="_blank">http://goo.gl/it488V</a> for more information.</div><div dir="ltr">==</div><div dir="ltr"><br></div><div dir="ltr">Ing. Daniele Romagnoli</div><div dir="ltr">Senior Software Engineer</div><div dir="ltr"><br></div><div dir="ltr">GeoSolutions S.A.S.</div><div dir="ltr">Via di Montramito 3/A</div><div dir="ltr">55054 Massarosa (LU)</div><div dir="ltr">Italy</div><div dir="ltr">phone: +39 0584 962313</div><div dir="ltr">fax: +39 0584 1660272</div><div dir="ltr"><br></div><div dir="ltr"><a href="http://www.geo-solutions.it" target="_blank">http://www.geo-solutions.it</a></div><div dir="ltr"><a href="http://twitter.com/geosolutions_it" target="_blank">http://twitter.com/geosolutions_it</a></div><div dir="ltr"><br></div><div dir="ltr"><div dir="ltr"><span style="font-size:12.8px">-------------------------------------------------------</span></div><div dir="ltr"><span style="font-size:12.8px"><br></span></div><div dir="ltr"><span style="font-size:12.8px">Con riferimento alla normativa sul trattamento dei dati personali (Reg. 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