Description

Return the convex hull geometry of the raster excluding NODATA pixels. If nband is NULL, all bands of the raster are considered.

Availability: 2.1.0

Examples

WITH foo AS (
	SELECT
		ST_SetValues(
			ST_SetValues(
				ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(9, 9, 0, 0, 1, -1, 0, 0, 0), 1, '8BUI', 0, 0), 2, '8BUI', 1, 0),
				1, 1, 1,
				ARRAY[
					[0, 0, 0, 0, 0, 0, 0, 0, 0],
					[0, 0, 0, 0, 0, 0, 0, 0, 0],
					[0, 0, 0, 0, 0, 0, 0, 0, 0],
					[0, 0, 0, 1, 0, 0, 0, 0, 1],
					[0, 0, 0, 1, 1, 0, 0, 0, 0],
					[0, 0, 0, 1, 0, 0, 0, 0, 0],
					[0, 0, 0, 0, 0, 0, 0, 0, 0],
					[0, 0, 0, 0, 0, 0, 0, 0, 0],
					[0, 0, 0, 0, 0, 0, 0, 0, 0]
				]::double precision[][]
			),
			2, 1, 1,
			ARRAY[
				[0, 0, 0, 0, 0, 0, 0, 0, 0],
				[0, 0, 0, 0, 0, 0, 0, 0, 0],
				[0, 0, 0, 0, 0, 0, 0, 0, 0],
				[1, 0, 0, 0, 0, 1, 0, 0, 0],
				[0, 0, 0, 0, 1, 1, 0, 0, 0],
				[0, 0, 0, 0, 0, 1, 0, 0, 0],
				[0, 0, 0, 0, 0, 0, 0, 0, 0],
				[0, 0, 0, 0, 0, 0, 0, 0, 0],
				[0, 0, 1, 0, 0, 0, 0, 0, 0]
			]::double precision[][]
		) AS rast
)
SELECT
	ST_AsText(ST_ConvexHull(rast)) AS hull,
	ST_AsText(ST_MinConvexHull(rast)) AS mhull,
	ST_AsText(ST_MinConvexHull(rast, 1)) AS mhull_1,
	ST_AsText(ST_MinConvexHull(rast, 2)) AS mhull_2
FROM foo

               hull               |                mhull                |               mhull_1               |               mhull_2
----------------------------------+-------------------------------------+-------------------------------------+-------------------------------------
 POLYGON((0 0,9 0,9 -9,0 -9,0 0)) | POLYGON((0 -3,9 -3,9 -9,0 -9,0 -3)) | POLYGON((3 -3,9 -3,9 -6,3 -6,3 -3)) | POLYGON((0 -3,6 -3,6 -9,0 -9,0 -3))
					

See Also

ST_Envelope, ST_ConvexHull, ST_ConvexHull, ST_AsText