[QGIS-Developer] Reg: QgsCoordinateTransform not working on Linux

[Prem Kumar]

the OperationResult value is 0 - zero in both windows and linux cases.
Although I could not verify in QGIS Python console from Linux as it is on a
server machine, I have verified the same on my personal macbook pro where
the same code works perfectly fine from QGIS Console but not from pycharm -
similar to Linux.

Since I was running after deliverables, I had taken an alternative approach
to transform the data by pyproj for the time being, but I'm not sure what
is missing in QgsApplication that it could not transform the geometry. In
fact, I have transformed each point and prepared the line, still the same
behavior.

-Prem


On Thu, May 27, 2021 at 7:50 PM Ujaval Gandhi <ujaval at spatialthoughts.com>
wrote:

> OK. Test the code in  QGIS Python Console. If that works, you have a
> problem with initialization. If that also doesn't work, print the result of
> the transform which will give you the OperationResult (Explanation at
> https://qgis.org/api/classQgsGeometry.html#a8baf383b737d73cafeabe09f5b0d7ef7)
> that may give insight into the issue.
>
> Ujaval Gandhi
> Spatial Thoughts
>
> On Thu, May 27, 2021, 7:42 PM Prem Kumar <prem.netgis at gmail.com> wrote:
>
>> Hi Ujaval,
>>
>> Thanks for your reply. I have made the suitable code changes as you have
>> suggested but I still see the same behaviour.
>>
>> In fact, the given code snippet in the email is an extract from my
>> overall code where proper initialisation and disposing of qgis application
>> object is followed. The only difference between running the script on
>> windows and linux is that, Im running the script on linux machine in a
>> python virtual environment where as windows, running it directly from qgis
>> python distributable. Some additional information and thanks for the
>> troubleshoot option.
>>
>> *Windows:*
>> OS: Microsoft Windows 10 Enterprise
>> QGIS: 3.10.10-A Coruña
>> Python: Python 3.7.0
>>
>> *Linux: *
>> OS Kernel: Ubuntu 18.04.3 LTS
>> QGIS: '3.16.3-Hannover'
>> Python: Python 3.6.9
>>
>> -Prem
>>
>>
>>
>>
>>
>>
>>
>> On Thu, May 27, 2021 at 6:50 PM Ujaval Gandhi <ujaval at spatialthoughts.com>
>> wrote:
>>
>>> You are not initializing QGIS in your script. Try adding this at the
>>> beginning of your script
>>>
>>> from qgis.core import QgsApplication
>>>
>>> qgs = QgsApplication([], False)
>>> qgs.initQgis()
>>>
>>> [image: Logo] <https://spatialthoughts.com/>
>>> Ujaval Gandhi
>>> Spatial Thoughts
>>> mobile: +91-8095684687
>>> email: ujaval at spatialthoughts.com
>>> [image: LinkedIn icon] <https://www.linkedin.com/in/spatialthoughts/>  [image:
>>> Twitter icon] <https://twitter.com/spatialthoughts>
>>>
>>>
>>>
>>> On Thu, May 27, 2021 at 6:27 PM Prem Kumar <prem.netgis at gmail.com>
>>> wrote:
>>>
>>>> Hi Team,
>>>>
>>>> Just wondering whether I'm missing something or a genuine bug, please
>>>> advise below.
>>>>
>>>> All I am trying is, to take the geometry object in json format whose
>>>> CRS is in WGS84 (EPSG:4326) and transform the geometry to EPSG:3857 CRS and
>>>> eventually use it in further processing because rest of the processing is
>>>> in EPSG:3857 CRS.
>>>>
>>>> I have written below code and it works like a charm on Windows 10 but
>>>> it doesn't transform the geometry on Linux. Please advise if there is
>>>> anything wrong or missing to add.
>>>> *Code Snippet for reproducing:*
>>>>
>>>> from qgis.PyQt.QtCore import QVariant
>>>> from shapely.geometry import shape
>>>> import geojson,json
>>>> from qgis.core import (QgsGeometry,QgsCoordinateReferenceSystem,QgsCoordinateTransform,QgsProject)
>>>> from shapely import speedups as sups
>>>> sups.disable()
>>>>
>>>> in_geometry='[{"type": "LineString","coordinates": [[-78.85338577199997,43.85845267000008],[-78.85593885699996,43.857924291000074]]}]'
>>>> geomjson = json.loads(in_geometry)
>>>> old_crs = QgsCoordinateReferenceSystem("EPSG:4326")
>>>> new_crs = QgsCoordinateReferenceSystem("EPSG:3857")
>>>> xtransform = QgsCoordinateTransform(old_crs, new_crs, QgsProject.instance())
>>>> for i, g in enumerate(geomjson):
>>>>     s = json.dumps(g)
>>>>     g1 = geojson.loads(s)
>>>>     shapely_geom = shape(g1)
>>>>     qgs_geom=QgsGeometry.fromWkt(shapely_geom.wkt)
>>>>     qgs_geom.transform(xtransform)
>>>>     print (qgs_geom)
>>>>
>>>> *Output from Pycharm:*
>>>> C:\Qgis\apps\Python37\python.exe C:/_WORK/SERVICE/test_transform.py
>>>> <QgsGeometry: LineString (-8777918.77684544585645199
>>>> 5443563.52439526654779911, -8778202.97550544328987598
>>>> 5443481.85537817236036062)>
>>>>
>>>> Process finished with exit code 0
>>>>
>>>> *Output from Linux terminal:*
>>>> (gisenv) admin at rd-temp-server:~/gis_service$ python3 test_transform.py
>>>> Application path not initialized
>>>> Application path not initialized
>>>> <QgsGeometry: LineString (-78.85338600000000042 43.85845299999999725,
>>>> -78.85593900000000644 43.85792399999999702)>
>>>> (gisenv) admin at rd-temp-server:~/gis_service$
>>>>
>>>> Thanks.
>>>> -Prem
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>>>
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