Re: [QGIS-Developer] PYQGIS - Numpy array to QgsRasterLayer without writing to file first
Hi Benjamin,
This does appear to work, I am now able to use vsimem file handlers with
gdal rasters to go from numpy arrays to qgis raster layers effectively.
Very exciting, thanks for this tip! I had another QGIS dev question, but I
will start a new thread for that.
For anyone else, this is all that I did:
dataset = gdal_driver.Create('/vsimem/imagetst.tif', cols, rows, no_bands,
gdal.GDT_Float32, creation_options)
...write array to band, set geotransform, etc
rlayer = QgsRasterLayer('/vsimem/imagetst.tif', 'imagetst', 'gdal')
Thanks again,
Eric
On Wed, Mar 3, 2021 at 12:57 AM Benjamin Jakimow <
benjamin.jaki...@geo.hu-berlin.de> wrote:
> Hi Eric,
>
> you might try to use a /vsimem/ path. For example, save your image to
> "/vsimem/myimage.tif" and
> open it as QgsRasterLayer. I haven't tested it with gdal.Datasets, but it
> works with with ogr.DataSources.
> Probably you shouldn't overwrite or delete the "/vsimem" object while QGIS
> has still a reference on it.
>
> More details here:
> https://gdal.org/user/virtual_file_systems.html#vsimem-in-memory-files
>
> Greetings,
>
> Benjamin
>
> On 2021-03-03 00:00, Eric Younkin - NOAA Federal wrote:
>
> Hello,
>
> I've been trying to figure out how to draw grids and lines from numpy
> arrays without driving to a raster/vector file first. I tried using the
> gdal 'MEM' driver to make a gdal Dataset from a numpy array and pass that
> in as a QgsRasterLayer, I get the following:
>
> >>> memobj
> at 0x019B3131AC30> >
> >>> QgsRasterLayer(memobj, 'testlayer', 'gdal')
> Traceback (most recent call last):
> File "", line 1, in
> TypeError: QgsRasterLayer(): arguments did not match any overloaded call:
> overload 1: too many arguments
> overload 2: argument 1 has unexpected type 'Dataset'
>
> The only other approach that I could find was:
>
>
> https://gis.stackexchange.com/questions/201804/how-to-create-raster-layer-directly-from-numpy-array-in-qgis-without-saving-to
>
> but I suspect that the return from the processing.run command is probably
> a temp file, so it is still going to file. Is there not a way to generate
> a raster layer from a numpy array without writing to file first?
>
> Thanks,
> Eric
>
> --
> Eric Younkin
> Physical Scientist
> NOAA OCS, Hydrographic Systems and Technology Branch
> 1315 East-West Highway
> N/CS11, Room 6604
> Silver Spring, MD 20910
> Office: 240-847-8208
> Cell: 828-331-8197
>
> ___
> QGIS-Developer mailing list
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>
>
> --
> --
> Benjamin Jakimow, Doctoral Researcher
> Earth Observation Lab | Geography Department | Humboldt-Universität zu
> Berlin
>
> e-mail: benjamin.jaki...@geo.hu-berlin.de
>
> phone: +49 (0) 30 2093 6894
> mobile: +49 (0) 157 5656 8477
> fax:+49 (0) 30 2093 6848
> mail: Unter den Linden 6 | 10099 Berlin | Germany
> room: 2'222
>
--
Eric Younkin
Physical Scientist
NOAA OCS, Hydrographic Systems and Technology Branch
1315 East-West Highway
N/CS11, Room 6604
Silver Spring, MD 20910
Office: 240-847-8208
Cell: 828-331-8197
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Re: [QGIS-Developer] PYQGIS - Numpy array to QgsRasterLayer without writing to file first
Hi Eric, you might try to use a /vsimem/ path. For example, save your image to "/vsimem/myimage.tif" and open it as QgsRasterLayer. I haven't tested it with gdal.Datasets, but it works with with ogr.DataSources. Probably you shouldn't overwrite or delete the "/vsimem" object while QGIS has still a reference on it. More details here: https://gdal.org/user/virtual_file_systems.html#vsimem-in-memory-files Greetings, Benjamin On 2021-03-03 00:00, Eric Younkin - NOAA Federal wrote: Hello, I've been trying to figure out how to draw grids and lines from numpy arrays without driving to a raster/vector file first. I tried using the gdal 'MEM' driver to make a gdal Dataset from a numpy array and pass that in as a QgsRasterLayer, I get the following: memobj *' at 0x019B3131AC30> > QgsRasterLayer(memobj, 'testlayer', 'gdal') Traceback (most recent call last): File "", line 1, in TypeError: QgsRasterLayer(): arguments did not match any overloaded call: overload 1: too many arguments overload 2: argument 1 has unexpected type 'Dataset' The only other approach that I could find was: https://gis.stackexchange.com/questions/201804/how-to-create-raster-layer-directly-from-numpy-array-in-qgis-without-saving-to but I suspect that the return from the processing.run command is probably a temp file, so it is still going to file. Is there not a way to generate a raster layer from a numpy array without writing to file first? Thanks, Eric -- Eric Younkin Physical Scientist NOAA OCS, Hydrographic Systems and Technology Branch 1315 East-West Highway N/CS11, Room 6604 Silver Spring, MD 20910 Office: 240-847-8208 Cell: 828-331-8197 ___ QGIS-Developer mailing list QGIS-Developer@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer -- -- Benjamin Jakimow, Doctoral Researcher Earth Observation Lab | Geography Department | Humboldt-Universität zu Berlin e-mail: benjamin.jaki...@geo.hu-berlin.de phone: +49 (0) 30 2093 6894 mobile: +49 (0) 157 5656 8477 fax:+49 (0) 30 2093 6848 mail: Unter den Linden 6 | 10099 Berlin | Germany room: 2'222___ QGIS-Developer mailing list QGIS-Developer@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
[QGIS-Developer] PYQGIS - Numpy array to QgsRasterLayer without writing to file first
Hello, I've been trying to figure out how to draw grids and lines from numpy arrays without driving to a raster/vector file first. I tried using the gdal 'MEM' driver to make a gdal Dataset from a numpy array and pass that in as a QgsRasterLayer, I get the following: >>> memobj > >>> QgsRasterLayer(memobj, 'testlayer', 'gdal') Traceback (most recent call last): File "", line 1, in TypeError: QgsRasterLayer(): arguments did not match any overloaded call: overload 1: too many arguments overload 2: argument 1 has unexpected type 'Dataset' The only other approach that I could find was: https://gis.stackexchange.com/questions/201804/how-to-create-raster-layer-directly-from-numpy-array-in-qgis-without-saving-to but I suspect that the return from the processing.run command is probably a temp file, so it is still going to file. Is there not a way to generate a raster layer from a numpy array without writing to file first? Thanks, Eric -- Eric Younkin Physical Scientist NOAA OCS, Hydrographic Systems and Technology Branch 1315 East-West Highway N/CS11, Room 6604 Silver Spring, MD 20910 Office: 240-847-8208 Cell: 828-331-8197 ___ QGIS-Developer mailing list QGIS-Developer@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
