[raster] ST_Clip

[pracine]

As a wrapper around ST_MapAlgebra optimized by ST_SetValues(raster, band, x ,y, width, height, raster2, band2).

We can then optimize ST_Intersection by cliping the intersecting area before polygonizing.

[robe]

Pierre already has this committed in trunk. I haven't had a chance to look at it but on my todo.

[dustymugs]

From the looks of it, Pierre's ST_Clip has the following signatures.

1. ST_Clip(
	rast raster, band int,
	geom geometry,
	nodata float8 DEFAULT null,
	trimraster boolean DEFAULT false
)

2. ST_Clip(
	rast raster,
	geom geometry,
	nodata float8 DEFAULT null,
	trimraster boolean DEFAULT false
)

3. ST_Clip(
	rast raster, band int,
	geom geometry,
	trimraster boolean
)

4. ST_Clip(
	rast raster,
	geom geometry,
	trimraster boolean
)

I'm wondering if the "nodata" parameter could be dropped as I would consider ST_Clip a pure extent constraining function with no data manipulation. Also, I'd like to see trimraster default to TRUE as the primary purpose of ST_Clip is to cut up the raster to only the area(s) of interest. Will need to ask postgis-devel as there are one or two users of ST_Clip.

[dustymugs]

After doing some digging, I'm leaving Pierre's set of ST_Clip functions as is. Just need to add regression tests.

[pracine]

regression tests added in r9181. Closing.