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

[Joaquim Manuel Freire Luís]

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 !



OK, I owe you at least that. It's just a heavy first step (fork+PR) for this small thing but I'll do it.





"OGR_G_GetX() Fetch the x coordinate of a point from a geometry."


From: Even Rouault <even.rouault at spatialys.com><mailto:even.rouault at spatialys.com>
Sent: Monday, March 29, 2021 4:43 PM
To: Joaquim Manuel Freire Luís <jluis at ualg.pt><mailto:jluis at ualg.pt>; gdal-dev at lists.osgeo.org<mailto: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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