[Qgis-user] NoData in RGB Imagery

[Richard McDonnell]

Hi Johannes,
Thanks for getting back to me. In general we would use the same value for each band, so 256 or -9999. We only work, where possible with GeoTIFF, so the Internal Mask idea is a nice one I hadn’t thought of. Also the use of an ALPHA channel, might be an option.

I could be wrong, but in relation to the internal masking, I believe it can be difficult for some CAD and GI Software to recognise internal masking, I believe there’s even an issue with GeoServer, which we use extensively here. As you say an Alpha Band is also an option…I will need to experiment a little more!
Once again, thank you for your response!
Regards,

Richard.




——
Richard McDonnell MSc GIS, FME Certified Professional
FRM Data Management

——
Oifig na nOibreacha Poiblí
Office of Public Works

Sráid Jonathan Swift, Baile Átha Troim, Co na Mí, C15 NX36
Jonathan Swift Street, Trim, Co Meath, C15 NX36
——
M +353 87 688 5964 T +353 46 942 2409
https://gov.ie/opw

——
To send me files larger than 30MB, please use the link below https://filetransfer.opw.ie/filedrop/richard.mcdonnell@opw.ie

Email Disclaimer: https://www.gov.ie/en/organisation-information/439daf-email-disclaimer/
From: Johannes Kröger (WhereGroup) <johannes.kroeger at wheregroup.com>
Sent: 14 January 2022 09:39
To: Richard McDonnell <richard.mcdonnell at opw.ie>; Qgis Users List <qgis-user at lists.osgeo.org>
Subject: Re: [Qgis-user] NoData in RGB Imagery


Hey Richard,

do you have different NODATA pixels between the three bands (R, G, B) or is it the same? If there are no differences then you can use an additional channel as mask. I would suggest you store your imagery in GeoTIFF with an "internal mask". Even posted a nice example of this in https://lists.osgeo.org/pipermail/gdal-dev/2014-August/039907.html
If your format supports RGBA (e.g. PNG), then that would be another way to achieve this but a nice GeoTIFF should be the best solution.

Cheers, Hannes
Am 13.01.22 um 18:35 schrieb Richard McDonnell:
Hi all,
I have a general GIS query and am hoping I can get some insight from the community.
It relates to how we deal with pixels with no data in RGB Imagery. It seems to be typical to produce RGB imagery as 8bit with pixel values between 0 and 255, with either 0 or 255 being used as the NoDATA value. To me this is problematic, as there can be valid pixels within your image with 0 or 255. To me the solution is to use 16bit Imagery and to assign the NoDATA value to any value outside of the 0 – 255 range.
I know in DEM’s its usual to use -9999 as your NoDATA value but my question is, Is there a standardised way to deal with NoDATA in RGB?

I welcome any comments and suggestions.
Regards & Thanks in advance,

Richard.



——
Richard McDonnell MSc GIS, FME Certified Professional
FRM Data Management

——
Oifig na nOibreacha Poiblí
Office of Public Works

Sráid Jonathan Swift, Baile Átha Troim, Co na Mí, C15 NX36
Jonathan Swift Street, Trim, Co Meath, C15 NX36
——
M +353 87 688 5964 T +353 46 942 2409
https://gov.ie/opw

——
To send me files larger than 30MB, please use the link below https://filetransfer.opw.ie/filedrop/richard.mcdonnell@opw.ie

Email Disclaimer: https://www.gov.ie/en/organisation-information/439daf-email-disclaimer/




_______________________________________________

Qgis-user mailing list

Qgis-user at lists.osgeo.org<mailto:Qgis-user at lists.osgeo.org>

List info: https://lists.osgeo.org/mailman/listinfo/qgis-user

Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

--

Johannes Kröger / GIS-Entwickler/-Berater

WhereGroup GmbH

Grevenweg 89

20537 Hamburg

Germany



Tel: +49 (0)228 / 90 90 38 - 36

Fax: +49 (0)228 / 90 90 38 - 11



johannes.kroeger at wheregroup.com<mailto:johannes.kroeger at wheregroup.com>

www.wheregroup.com<http://www.wheregroup.com>

Geschäftsführer:

Olaf Knopp, Peter Stamm

Amtsgericht Bonn, HRB 9885

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



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

Schon gewusst?


In unserem Blog geben wir Tipps & Tricks zu
 Open-Source-GIS-Software

und berichten aus unserem Experten-Alltag:

https://wheregroup.com/blog/

---------------------------------------------
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20220114/70bdca6b/attachment.html>