[gdal-dev] Can't access to points in a buffer returned geometry with OGR_G_GetX

[Even Rouault]

Le 29/03/2021 à 17:46, Joaquim Manuel Freire Luís a écrit :
>
> Thanks,
>
> Maybe add that info to the docs? By now it only says
>
We would definitely appreciate your contribution !

> “OGR_G_GetX() Fetch the x coordinate of a point from a geometry.”
>
> *From:*Even Rouault <even.rouault at spatialys.com>
> *Sent:* Monday, March 29, 2021 4:43 PM
> *To:* Joaquim Manuel Freire Luís <jluis at ualg.pt>; gdal-dev at lists.osgeo.org
> *Subject:* Re: [gdal-dev] Can't access to points in a buffer returned 
> geometry with OGR_G_GetX
>
> OGR_G_GetX() can only work on a Point or a LineString/LinearRing
>
> for a polygon, you need to extract the ring first with 
> OGR_G_GetGeometryRef() / OGR_G_GetGeometryCount()
>
> Even
>
> Le 29/03/2021 à 17:26, Joaquim Manuel Freire Luís a écrit :
>
>     OK, one more from the Julia wrappers. Playing with buffers now,
>     and it works but I want to get the points and that fails
>
>     julia> wkt = "POINT (1198054.34 648493.09)";
>
>     julia> dbf = Gdal.buffer(Gdal.fromWKT(wkt), 500)
>
>     Geometry: POLYGON ((1198554.34 648493.09,1198553.65476738 64 ... .09))
>
>     julia> toWKT(dbf)[1:90]
>
>     "POLYGON ((1198554.34 648493.09,1198553.65476738
>     648466.922021879,1198551.60094768 648440.8"
>
>     The ‘toWKT()’ function calls OGR_G_ExportToWkt()
>
>     But now if I try to extract the points with OGR_G_GetX() it errors
>
>     julia> Gdal.OGR_G_GetX(dbf.ptr, 0)
>
>     ERROR 6: Incompatible geometry for operation                    #
>     ç============= ????
>
>     0.0
>
>     julia> Gdal.OGR_G_GetPointCount(dbf.ptr)          # ç=============
>     Why so?
>
>     0
>
>     Although the toWKT() works, tat’s an ascii representation but I
>     want I want to access them in binary (not in WKB) to send to GMT.
>
>     Joaquim
>
>
>
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