[Qgis-user] How to make diagonals

[chris hermansen]

Might generalizing the lines (Poiker Douglas or similar) yield four line
rectangles?

On Thu, Feb 3, 2022, 23:44 Etienne Trimaille <etienne.trimaille at gmail.com>
wrote:

> Maybe "oriented_bbox" to get first a proper rectangle ?
>
> https://docs.qgis.org/testing/en/docs/user_manual/expressions/functions_list.html#oriented-bbox
>
> But then, you might have some tiny leftover. It depends if you care or not.
>
> Otherwise, you need to use the angle at each points.
>
> I thought there is the longest line possible within a polygon, but I can't
> find it. I did it manually a few years ago.
>
> Le jeu. 3 févr. 2022 à 23:29, Dario C <dario955i at gmail.com> a écrit :
>
>> Hi,
>> I have several rectangles (almost squared) and I'd like to represent
>> their diagonals.
>>
>> I started to do with geometry generator with:
>> make_line(point_n($geometry,1),point_n($geometry,4))
>> and
>> make_line(point_n($geometry,2),point_n($geometry,5))
>>
>> Unfortunately, even if they look rectangular, actually they have more
>> then 4 points and, moreover, points do not always have the same order.
>>
>> here below an example:
>> [image: image.png]
>>
>> Is there any expression in order to pick the two longest segments
>> connecting all the points of the geometry?
>>
>>
>> Thanks
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