ST_Envelope-PolarDB(PolarDB)-阿里云帮助中心

Calculates the bounding rectangle of a raster object from its georeferencing information.

Syntax

geometry ST_Envelope(raster source);
geometry ST_Envelope(raster source,
                     integer pyramid);

Parameters

Parameter Name	Description
source	The raster object for the calculation.
pyramid	The pyramid level. Valid values start from 0. The default value is 0.

Description

The area outlined in red in the following figure is the bounding box of the raster object.

Bounding box

Example

SELECT st_astext(st_envelope(rast_object)) FROM raster_table;

----------------------------------------------------
 POLYGON((-180 90,180 90,180 -90,-180 -90,-180 90))

-- Specify the pyramid level                 
SELECT st_astext(st_envelope(rast_object,  1)) FROM raster_table;

----------------------------------------------------
 POLYGON((-180 90,180 90,180 -90,-180 -90,-180 90))