ST_MakeEmptyRaster
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Name

ST_MakeEmptyRaster — Returns an empty raster (having no bands) of given dimensions (width & height), upperleft X and Y, pixel size and rotation (scalex, scaley, skewx & skewy) and reference system (srid). If a raster is passed in, returns a new raster with the same size, alignment and SRID. If srid is left out, the spatial ref is set to unknown (0).

Synopsis

raster ST_MakeEmptyRaster(raster rast);

raster ST_MakeEmptyRaster(integer width, integer height, float8 upperleftx, float8 upperlefty, float8 scalex, float8 scaley, float8 skewx, float8 skewy, integer srid=unknown);

raster ST_MakeEmptyRaster(integer width, integer height, float8 upperleftx, float8 upperlefty, float8 pixelsize);

Description

Returns an empty raster (having no band) of given dimensions (width & height) and georeferenced in spatial (or world) coordinates with upper left X (upperleftx), upper left Y (upperlefty), pixel size and rotation (scalex, scaley, skewx & skewy) and reference system (srid).

The last version use a single parameter to specify the pixel size (pixelsize). scalex is set to this argument and scaley is set to the negative value of this argument. skewx and skewy are set to 0.

If an existing raster is passed in, it returns a new raster with the same meta data settings (without the bands).

If no srid is specified it defaults to 0. After you create an empty raster you probably want to add bands to it and maybe edit it. Refer to ST_AddBand to define bands and ST_SetValue to set initial pixel values.

Examples

Use an existing raster as a template and output metadata of the rasters we added.

Code
INSERT INTO dummy_rast(rid, rast)
VALUES(3, ST_MakeEmptyRaster(100, 100, 0.0005, 0.0005, 1, 1, 0, 0, 4326) );
INSERT INTO dummy_rast(rid, rast)
SELECT 4, ST_MakeEmptyRaster(rast)
FROM dummy_rast WHERE rid = 3;
SELECT
    rid,
    (md).width,
    (md).height,
    (md).scalex,
    (md).scaley,
    (md).srid
FROM (
    SELECT rid, ST_MetaData(rast) AS md
    FROM dummy_rast
    WHERE rid IN (3, 4)
) AS foo
ORDER BY rid;
Output
 rid | width | height | scalex | scaley | srid
-----+-------+--------+--------+--------+------
   3 |   100 |    100 |      1 |      1 | 4326
   4 |   100 |    100 |      1 |      1 | 4326