[Qgis-user] extracting vertices from a multipolygon using Field Calculator Function Editor

[Stefan Giese (WhereGroup)]

as a starting point:

/from qgis.core import *//
//from qgis.gui import *//
//
//@qgsfunction(args='auto', group='Custom', referenced_columns=[])//
//def zCutBox(feature, parent)://
//    """//
//    Calculates vertices and return the x coordinate of the first as 
string//
//    """//
//    geom = feature.geometry()//
//    vertices = []//
//    for v in geom.vertices()://
//        vertices.append(v)//
//    return str(vertices[0].x())/

Am 18.10.2021 um 13:42 schrieb Zoltan:
> Hi Listers,
> I can't for the life of me work out the syntax/commands to use in the 
> FieldCalculator->FunctionEditor for extracting vertices.
>
> I have a Polygon layer with Multipolygon rectangles at various rotations.
> I need to extract the 4 corner points so that I can calculate (and 
> save in a virtual layer) lines that I can later use with 
> "Processing->Split with lines".
>
> I will google for opening a new virtual layer and saving lines to it, 
> but if that is quick and easy then some help there would also be welcome.
>
> Please can someone point me to a sample functions covering these 
> requirements, or just fill in the gaps below.
> No, I'm not asking for someone to just write it for me.
>
> Thanks in advance,
> Zoltan
> [Having a brain-dead day :-(  ]
>
>
>     from qgis.core import *
>     from qgis.gui import *
>
>     @qgsfunction(args='auto', group='Custom', referenced_columns=[])
>     def zCutBox(feature, parent):
>         vertices =
>
>         blah blah
>         return vertices[0][0]
>
>
> -- 
>
> =============================================
> Zoltan Szecsei GPrGISc 0031
> Geograph (Pty) Ltd.
> GIS and Photogrammetric Services
>
> Cape Town, South Africa.
>
> Mobile: +27-83-6004028 (Signal, not WhatsApp)
> www.geograph.co.za
> =============================================
>
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-- 
Mit freundlichen Grüßen
Stefan Giese
Projektleiter/Consultant

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