[QGIS-Developer] Offset lines via qgis python

[Ujaval Gandhi]

You can look at the implementation
<https://github.com/qgis/QGIS/blob/2d1aa68f0d044f2aced7ebeca8d2fa6b754ac970/src/analysis/processing/qgsalgorithmoffsetlines.cpp>
of offsetline algorithm and you'll notice that it
uses geometry.offsetCurve(). You can do the same in your code.
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Ujaval Gandhi
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On Wed, Jun 9, 2021 at 1:31 PM Prem Kumar <prem.netgis at gmail.com> wrote:

> Hi Team,
>
> Just wondering if there is a python api which gets an offset line or
> parallel line (to both left and right sides) to a given line geometry in
> Qgis Python. I know there exists a processing tool called Offsetlines
> <https://docs.qgis.org/3.16/en/docs/user_manual/processing_algs/qgis/vectorgeometry.html#offset-lines> but
> need this similar functionality at geometry object level so that I can
> create offset lines only when needed based on my logic.
>
> The only way now is that I can perform the Offset lines on the entire
> layer and then access the offset geometry if needed.
>
> On other hand, shapely has parallel_offset
> <https://shapely.readthedocs.io/en/stable/manual.html#object.parallel_offset> but
> this needs conversion from shapely geometry to qgisgeometry.
>
> Just looking for thoughts on this to optimize heavy geometry operations.
> Appreciate your help.
>
> -Prem
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