ST_AsGDALRaster
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Nome

ST_AsGDALRaster — Return the raster tile in the designated GDAL Raster format. Raster formats are one of those supported by your compiled library. Use ST_GDALDrivers() to get a list of formats supported by your library.

Sinopse

bytea ST_AsGDALRaster(raster rast, text format, text[] options=NULL, integer srid=sameassource);

Description

Retorna a tile raster no formato designado. Os argumentos estão listados abaixo:

  • format formato para saída. Isso depende dos drivers compilados na sua biblioteca libgdal. Estão normalmente disponíveis 'JPEG', 'GTIff', 'PNG'. Use ST_GDALDrivers para conseguir uma lista dos formatos suportados por sua biblioteca.

  • options texto arranjo de opções GDAL. As opções válidas são dependentes do formato. Recorra a GDAL Raster format options para mais detalhes.

  • srid the spatial reference identifier to embed in the output raster

Disponibilidade: 2.0.0 - requer GDAL >= 1.6.0.

Exemplos

Export multiple raster tiles as a single JPEG image with 50 percent quality.

Code
SELECT ST_AsGDALRaster(ST_Union(rast), 'JPEG', ARRAY['QUALITY=50']) As rastjpg
FROM dummy_rast
WHERE rast && ST_MakeEnvelope(10, 10, 11, 11);

One way to export raster into another format is using PostgreSQL large object export functions. The following repeats the JPEG example and exports the result. Note that this requires superuser access because it uses server-side large object functions. It will also export to path on server network. If you need export locally, use the psql equivalent lo_ functions which export to the local file system instead of the server file system.

Code
DROP TABLE IF EXISTS tmp_out ;

CREATE TABLE tmp_out AS
SELECT lo_from_bytea(
       0,
       ST_AsGDALRaster(ST_Union(rast), 'JPEG', ARRAY['QUALITY=50'])
        ) AS loid
  FROM dummy_rast
WHERE rast && ST_MakeEnvelope(10, 10, 11, 11);

SELECT lo_export(loid, '/tmp/dummy.jpg')
   FROM tmp_out;

SELECT lo_unlink(loid)
  FROM tmp_out;

Export a raster as a GeoTIFF using the default creation options.

Code
SELECT ST_AsGDALRaster(rast, 'GTiff') AS rasttiff
FROM dummy_rast WHERE rid = 2;

Export a GeoTIFF using JPEG compression at 90 percent quality and embed SRID 4269.

Code
SELECT ST_AsGDALRaster(
  rast,
  'GTiff',
  ARRAY['COMPRESS=JPEG', 'JPEG_QUALITY=90'],
  4269) AS rasttiff
FROM dummy_rast WHERE rid = 2;