[postgis-devel] Proposal: Adding buffer parameter to ST_TileEnvelope()

Paul Ramsey pramsey at cleverelephant.ca
Wed Nov 13 10:15:03 PST 2019


“gutter”? “margin”? “padding”?
In css terms, margin is the closest.
P

> On Nov 13, 2019, at 12:13 PM, Yuri Astrakhan <yuriastrakhan at gmail.com> wrote:
> 
> I am thinking of the percentage in terms of linear bounding box side shift in the outwards direction, so buffer=0.5 would make each side shift outwards by half a tile size, thus producing a box 2x2 of the original tile == 4x increase in the tile area.  Buffer might be a bad word for this parameter?
> 
> On Wed, Nov 13, 2019 at 1:04 PM <rmrodriguez at carto.com <mailto:rmrodriguez at carto.com>> wrote:
> On Wed, Nov 13, 2019 at 6:44 PM Yuri Astrakhan <yuriastrakhan at gmail.com <mailto:yuriastrakhan at gmail.com>> wrote:
> >
> > Michael, thank you for your example. Per Paul's previous email, it made me realize that unlike ST_AsMVTGeom, ST_TileEnvelope does not need to understand the concept of extent (internal "pixels"), but instead can work just as well with percentages.
> >
> > Updated proposal:   buffer is a percentage increase of the original tile, limited to SRID space.  E.g.  buffer=0.5 would grow the tile by 50%, but if zoom=0, it would not grow at all.  If the tile is on the edge (e.g. 0,0), growing it should extend the longitude across the anti-meridian line, but should not grow northwards (srid limit).
> 
> 
> Would that be 0.5x bigger area or 50% bigger sides, thus being 1.25x
> bigger area?
> 
> 
> -- 
> Raúl Marín Rodríguez
> carto.com <http://carto.com/>
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