[postgis-devel] wktraster ST_ConvexHull

Pierre Racine Pierre.Racine at sbf.ulaval.ca
Tue Apr 6 09:54:32 PDT 2010

>So the ST_ConvexHull is really only useful if you have an irregularly shaped
>raster or a rotated raster which I guess I don't commonly run into.


>The ST_AsPolygon I guess I also got wrong.  I keep on thinking about it as
>what is referred to as ST_Shape except my concept of ST_Shape would take all
>bands (leaving out nodata)  into consideration instead of a specific.

I suggested in february that we could rename ST_Shape to ST_Outline. But got no further feedback. Should we?

>Would seem better to call ST_AsPolygon - ST_DumpPolygons or something like
>that as it seems to be more in line with the PostGIS concept of  ST_Dump,
>ST_DumpRings, ST_DumpPoints... that return geometry_dump.

I never liked PostGIS ST_Dump.... Seems to me that ST_AsSimplePolygons() or ST_SingleParts() would be much more meaningful... We could add an "s" though to ST_AsPolygons().

>The distinction I see  it would always return a dump of polygons rather than
>an arbitrary dump of geometries
>And the path value would be replaced with a pixel value.

One problem I see is that people see the result of ST_Dump as simple polygons when the result of ST_AsPolygon is not necessarily simple polygons. You get simple polygons only when you add the 'CONTIGUOUS' keyword to the function (ST_AsPolygon(raster, integer, 'CONTIGUOUS')).

>Getting to names -- ST_AsWKTPolygon should not start with an ST_ if it is
>not intended for end user use.

Jorge, could we rename ST_AsWKTPolygon to RasterAsWKTPolygon?


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