[gdal-dev] mosaicking files with partial overlap and binary mask

Thu Jan 28 01:12:21 PST 2021

Hi Patrick,
nice!
Thanks for the feedback.

Do you have any info about eventual backports to previous versions?

Regards,
Daniele

On Thu, Jan 28, 2021 at 12:02 AM Patrick Young <
patrick.mckendree.young at gmail.com> wrote:

> Hi Daniele,
>
> Even added this functionality to VRTs just recently, see
>
> https://lists.osgeo.org/pipermail/gdal-dev/2020-December/053178.html
>
> I think it is slated for GDAL 3.3 but you could always build the bleeding
> edge.
>
> Patrick
>
> On Wed, Jan 27, 2021 at 3:50 AM Daniele Romagnoli <
> daniele.romagnoli at geo-solutions.it> wrote:
>
>> Hi list,
>> 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.
>> 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.
>>
>> Now I need to create a single TIF from all of these images.
>> I have tried with gdalbuildvrt but it doesn't produce good result.
>> Checking the doc I saw this:
>>
>>
>> *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.  *
>>
>> So I think it's expected and I have switched to gdal_merge.py.
>> 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:
>> - the inner group of N files get merged using the binary mask to a bigger
>> file.
>> - all the M bigger files get mosaicked again to a single huge file.
>>
>> I will spend some more time in testing different attempts.
>> In the meantime, do you have any suggestion or past experience on how to
>> deal with that?
>> 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).
>>
>> Thanks in advance.
>> Regards,
>> Daniele
>>
>>
>>
>>
>> --
>> Regards,
>> Daniele Romagnoli
>> ==
>> 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
>>
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-- 
Regards,
Daniele Romagnoli
==
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

-------------------------------------------------------

Con riferimento alla normativa sul trattamento dei dati personali (Reg. UE
2016/679 - Regolamento generale sulla protezione dei dati “GDPR”), si
precisa che ogni circostanza inerente alla presente email (il suo
contenuto, gli eventuali allegati, etc.) è un dato la cui conoscenza è
riservata al/i solo/i destinatario/i indicati dallo scrivente. Se il
messaggio Le è giunto per errore, è tenuta/o a cancellarlo, ogni altra
operazione è illecita. Le sarei comunque grato se potesse darmene notizia.

This email is intended only for the person or entity to which it is
addressed and may contain information that is privileged, confidential or
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European Regulation 2016/679 “GDPR” - copying, dissemination or use of this
e-mail or the information herein by anyone other than the intended
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