Expose makeValid

[tdunning]

I see that there is a function LibGEOS.GEOSMakeValid in the generated code.

Unfortunately, when I call it like LibGEOS.GEOSMakeValid(Ref(p)) where p is a self-intersecting polygon, I get back a null pointer.

This would be a very nice function to have working, but I don't understand how call it (else I would have brought a pull request).

Is there any way to get this to work?

[jaakkor2]

Yes, doable. LibGEOS.GEOSMakeValid_r returns a pointer, maybe one should convert to Julia type based on LibGEOS.geomTypeId as the type of the output depends on the input.

makeValid(g) = LibGEOS.GEOSMakeValid_r(LibGEOS._context.ptr, g.ptr)
a = LibGEOS.Polygon([[[0.,0],[2,0],[2,2],[0,-1],[0,0]]])
isValid(a) # false
b = makeValid(a)
isValid(b) # true
LibGEOS.geomTypeId(b) # 6
writegeom(MultiPolygon(b))

outputs a multi-polygon

"MULTIPOLYGON (((0 0, 0.6666666666666667 0, 0 -1, 0 0)), ((2 0, 0.6666666666666667 0, 2 2, 2 0)))"

whereas a valid polygon results in a polygon

a2 = LibGEOS.Polygon([[[0.,0],[2,0],[2,2],[0,+1],[0,0]]])
isValid(a2) # true
b2 = makeValid(a2)
isValid(b2)  # true
LibGEOS.geomTypeId(b2) # 3
writegeom(Polygon(b2))

outputs

"POLYGON ((0 0, 2 0, 2 2, 0 1, 0 0))"

Not only polygons, many other geometry types are supported https://github.com/libgeos/geos/blob/main/src/operation/valid/MakeValid.cpp

[tdunning]

Brilliant.

Not sure where I went wrong when guessing how to call this, but this is very helpful. I will take a look at it and see if I can package your one liner as a pull request.

[jaakkor2]

Tests could come from https://github.com/libgeos/geos/blob/main/tests/unit/capi/GEOSMakeValidTest.cpp

There seems to be functions not yet wrapped GEOSMakeValidParams_create, GEOSMakeValidParams_setKeepCollapsed, GEOSMakeValidWithParams, ... . Maybe just one user-facing function makeValid and keyword arguments for parameters.

[jaakkor2]

LibGEOS.geomFromGEOS is the function to go from GEOS to geom.
Better one-liner

makeValid(g) = LibGEOS.geomFromGEOS(LibGEOS.GEOSMakeValid_r(LibGEOS._context.ptr, g.ptr))

[tdunning]

Nice. I notice that the related function getGeometries is also not wrapped. It seems like the natural one liner for that is getGeometries(x::AbstractMultiPolygon) = LibGEOS.geomFromGEOS.(LibGEOS.getGeometries(p2.ptr)) What is the thought about specializing on types that are from GeoInterface?

…

On Tue, Sep 7, 2021 at 6:57 PM Jaakko Ruohio ***@***.***> wrote: LibGEOS.geomFromGEOS is the function to go from GEOS to geom. Better one-liner makeValid(g) = LibGEOS.geomFromGEOS(LibGEOS.GEOSMakeValid_r(LibGEOS._context.ptr, g.ptr)) — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#90 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAB5E6VE5C2VLN32GMPDOCLUA27JDANCNFSM5DPKSTSA> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>.