[Qgis-user] R: Importing a raster into a Geopackage

Wed Dec 2 08:10:57 PST 2020

Hi Alberto,

Can I share the file and your question in the gdal dev group?  Perhaps they will have an answer to your problem. You can also do that yourself if you prefer.

Kirt, if you have time, can you do the same run with the data in my google link?  If you can’t duplicate the problem, then we will have a better idea if you share your QGIS version and OS. Perhaps there is change in the gdal version between both computers.

Nicolas Cadieux
https://gitlab.com/njacadieux

> Le 2 déc. 2020 à 10:11, Alberto Vavassori <alberto.vavassori at polimi.it> a écrit :
> 
> 
> Hi Kirk,
> I tried with another raster file that represents a temperature distribution (continuous values). In this case, when I import it into the Geopackage, I see the same issue that you have just described: minimum and maximum values in the legend change, but it seems that the actual values remain unchanged, thus correct. Unfortunately this is not the case of the land cover raster (discrete set of values) that I have shared with you: in this case, the raster characteristics change, as we have all noticed.
> Just another question, hoping that you might have an answer: is it possible to store the symbology of a raster file inside the Geopackage? I know that it is possible for vector data, by clicking on “Style > Save style” in the “Symbology” tab. But I cannot find a way to save the symbology in case of raster files.
> Thanks a lot.
> Alberto
>  
> Da: Qgis-user <qgis-user-bounces at lists.osgeo.org> Per conto di Kirk Schmidt
> Inviato: mercoledì 2 dicembre 2020 16:00
> A: Nicolas Cadieux <njacadieux.gitlab at gmail.com>; qgis-user at lists.osgeo.org
> Oggetto: Re: [Qgis-user] R: Importing a raster into a Geopackage
>  
> Hi all:
> 
> I ran the r.stats to get a list of each pixel value on my test data (A small DEM) before and after conversion to a geopackage (see second image below).  The values and summary stats are identical for the two rasters but the default legend entry has a different min and maximum value.  So, I can conclude that the data is being written correctly but the default display parameters for the geopackage  are different than a geotiff. 
> 
> Kirk
> 
>  
> 
> <image001.png>
> 
> <image002.png>
> 
> On 12/1/2020 3:24 PM, Nicolas Cadieux wrote:
> Hi,
> 
> I changed the link so you have access to more files.
> 
> https://drive.google.com/drive/folders/1fMl9odowUFFRQFK61rTxgHeom_D8ymN6?usp=sharing
> 
> Nicolas
> 
> On 2020-12-01 1:58 p.m., Kirk Schmidt wrote:
> Hi Nicolas
> 
> I did the same and the legend indicates a change magnitude but if I subtract the geopackage raster from the original, all pixels equal zero.
> 
> Kirk
> 
> On 12/1/2020 2:36 PM, Nicolas Cadieux wrote:
> Hi,
> 
> Tried this:
> 
> gdal_translate -of GPKG -b 1 C:/Users/Nicolas/Desktop/Land_cover_Corine2018.tif C:/Users/Nicolas/Desktop/test.gpkg
> 
> I read 4 band and still get data modifications.
> 
> Nicolas
> 
> On 2020-12-01 1:28 p.m., Kirk Schmidt wrote:
> Hi Nicolas:
> 
> try the -b 1 parameter.  I just tried this and wrote a single band raster from a 3 channel tiff.
> 
> Kirk
> 
> On 12/1/2020 2:03 PM, Nicolas Cadieux wrote:
> I tried
> 
> gdal_translate -of GPKG -co "BAND_COUNT=1" C:/Users/Nicolas/Desktop/Land_cover_Corine2018.tif C:/Users/Nicolas/Desktop/TEST.gpkg for the creation and
> 
> C:\>gdal_translate -of GPKG -co "TILE_FORMAT = TIFF" C:/Users/Nicolas/Desktop/Land_cover_Corine2018.tif C:/Users/Nicolas/Desktop/TEST.gpkg
> 
> Same problem.  I wonder if we need to change the reading options... https://gdal.org/drivers/raster/gpkg.html
> 
> "Opening options
> 
> By default, the driver will expose a GeoPackage dataset as a four band (Red,Green, Blue,Alpha) dataset, which gives the maximum compatibility with the various encodings of tiles that can be stored. It is possible to specify an explicit number of bands with the BAND_COUNT opening option."
> 
> The problem could be when QGIS Reads the file, not when it writes the file.  I explains why we see 4 bands but not why values are changing.  I would make a bug report or ask the question on the gdal dev group to get Even Rouault's attention.
> 
> Nicolas
> 
>  
> 
> On 2020-12-01 12:17 p.m., Sebastian Gutwein wrote:
> This looks like the same issue you are having. github.com/qgis/QGIS/issues/38227
> According to the documentation linked in the issue you need to set the band count to 1 otherwise it defaults to 4. 
> gdal.org/drivers/raster/gpkg.html
> I have not tried this to see if it works. 
>  
> On Tue, Dec 1, 2020 at 11:52 AM Nicolas Cadieux <njacadieux.gitlab at gmail.com> wrote:
> Hi,
> 
> Looking at it now.  I see what you see.  I will try a few things.
> 
> Nicolas
> 
> On 2020-12-01 11:42 a.m., Alberto Vavassori wrote:
> Hi Nicolas,
> thank you for the answer. I send the raster that I am interested in.
> Alberto
>  
> Da: Nicolas Cadieux <njacadieux.gitlab at gmail.com> 
> Inviato: martedì 1 dicembre 2020 17:40
> A: Alberto Vavassori <alberto.vavassori at polimi.it>
> Cc: qgis-user at lists.osgeo.org
> Oggetto: Re: [Qgis-user] Importing a raster into a Geopackage
>  
> Hi,
> 
> Send a sample data set if you can't figure it out.
> 
> Nicolas
> 
> On 2020-12-01 10:35 a.m., Nicolas Cadieux wrote:
> Hi,
> Perhaps this can help: https://gdal.orgdrivers/raster/gpkg.html
>  
> “Various kind of input datasets can be converted to GeoPackage raster :
> 
> ·        Single band grey level
> 
> ·        Single band with R,G,B or R,G,B,A color table
> 
> ·        Two bands: first band with grey level, second band with alpha channel
> 
> ·        Three bands: Red, Green, Blue
> 
> ·        Four band: Red, Green, Blue, Alpha
> 
> GeoPackage rasters only support Byte data type.”
> 
> My guess is that if the original raster does not correspond to one of the categories above, it will be converted to the closest format. 
> 
>  
> Nicolas Cadieux
> https://gitlab.com/njacadieux
>  
> 
> Le 1 déc. 2020 à 09:58, Alberto Vavassori <alberto.vavassori at polimi.it> a écrit :
> 
> Hello everybody. I have an issue regarding the Geopackage format. I have tried to import a singleband raster file (it represents the land cover, thus every pixel has a single integer value corresponding to the land cover class), but this operation seems to modify the raster characteristics: the raster becomes a 4-bands raster and the pixels values change accordingly (basically, the original raster is saved in the Geopackage as an RGB image). It seems to be a bug of QGIS. I have also tried to use GDAL translate through the processing toolbox of QGIS to convert the TIFF file to a Geopackage file, but the result is the same.
> Has anybody faced this problem? May anybody suggest a way to work this problem out?
> Thank you.
> Alberto
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> Nicolas Cadieux
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> Nicolas Cadieux
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> 
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> Kirk Schmidt, MScF, BScF, RPF
> General Manager
> Nortek Resource Solutions Inc.
> RR # 1
> Thorburn, NS
> B0K 1W0
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> Nicolas Cadieux
> https://gitlab.com/njacadieux
> 
> 
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> -- 
> Kirk Schmidt, MScF, BScF, RPF
> General Manager
> Nortek Resource Solutions Inc.
> RR # 1
> Thorburn, NS
> B0K 1W0
> Tel (902) 922.3607
> Email: kirk at nortekresources.com
> Web: www.nortekresources.com
> 
> 
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> -- 
> Nicolas Cadieux
> https://gitlab.com/njacadieux
> -- 
> Kirk Schmidt, MScF, BScF, RPF
> General Manager
> Nortek Resource Solutions Inc.
> RR # 1
> Thorburn, NS
> B0K 1W0
> Tel (902) 922.3607
> Email: kirk at nortekresources.com
> Web: www.nortekresources.com
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