Add BoundingDiagonal() method to Envelope
#489
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The main usecase for this method is to help a user construct a compact representation of an envelope, for example as WKB. Rather than encoding the polygon representation of the Envelope, the LineString representation can be used instead. The Polygon representation uses 89 bytes (1 for the byte order, 4 to encode the number of rings, 4 to encode the number of points in the outer ring, and then 80 to represent the 5 points in the ring itself). The LineString representation only uses 37 bytes (1 for the byte order, 4 to encode the number of points, and 32 to represent 2 points).
geom/type_envelope.go
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| @@ -295,3 +295,27 @@ func (e Envelope) box() (rtree.Box, bool) { | |||
| MaxY: e.maxY, | |||
| }, !e.IsEmpty() | |||
| } | |||
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| // BoundingDiagonal returns the LineString that goes from the minimum point in | |||
| // the Envelope to the point in the Envelope. If the envelope is degenerate and | |||
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from the minimum point in the Envelope to the point in the Envelope: to which point in the Envelope?
What do you think about describing this as a LineString going from the bottom-left vertex to the top-right vertex of the envelope? At least, that's my understanding of the code, but perhaps my understanding/terminology is too plebeian. 😅
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Ah, I should have said "from the minimum point in the Envelope to the maximum point in the Envelope".
What do you think about describing this as a LineString going from the bottom-left vertex to the top-right vertex of the envelope?
That would work if we could assume that geometries were always in a coordinate system where X increases from left to right and Y as you move up the map. WGS84 and the UTM projections are examples. Unfortunately it doesn't hold for other projections, such as Web Mertcator, which has Y increasing as you move down the map.
I've reworded the comment in 3046816 to explicitly refer to the Min and Max methods, which is uses to construct the LineString.
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Thanks for reviewing! 🙇 |
Description
The main usecase for this method is to help a user construct a compact representation of an envelope, for example as WKB. Rather than encoding the polygon representation of the Envelope, the LineString representation can be used instead.
The Polygon representation uses 89 bytes (1 for the byte order, 4 to encode the number of rings, 4 to encode the number of points in the outer ring, and then 80 to represent the 5 points in the ring itself). The LineString representation only uses 37 bytes (1 for the byte order, 4 to encode the number
of points, and 32 to represent 2 points).
Check List
Have you:
Added unit tests? Yes.
Add cmprefimpl tests? (if appropriate?) N/A
Updated release notes? (if appropriate?) Yes.
Related Issue
Benchmark Results
N/A, this is new functionality that doesn't have benchmark tests.