ST_AsPNG — Return the raster tile selected bands as a single portable network graphics (PNG) image (byte array). If 1, 3, or 4 bands in raster and no bands are specified, then all bands are used. If more 2 or more than 4 bands and no bands specified, then only band 1 is used. Bands are mapped to RGB or RGBA space.
bytea
ST_AsPNG
(
raster
rast
, text[]
options=NULL
)
;
bytea
ST_AsPNG
(
raster
rast
, integer
nband
, integer
compression
)
;
bytea
ST_AsPNG
(
raster
rast
, integer
nband
, text[]
options=NULL
)
;
bytea
ST_AsPNG
(
raster
rast
, integer[]
nbands
, integer
compression
)
;
bytea
ST_AsPNG
(
raster
rast
, integer[]
nbands
, text[]
options=NULL
)
;
Returns the selected bands of the raster as a single Portable Network Graphics Image (PNG). Use
ST_AsGDALRaster
if you need to export as less common raster types. If no band is specified, then the first 3 bands are exported. There are many variants of the function with many options. If no
srid
is specified then then srid of the raster is used. These are itemized below:
nband
is for single band exports.
nbands
is an array of bands to export (note that max is 4 for PNG) and the order of the bands is RGBA. e.g ARRAY[3,2,1] means map band 3 to Red, band 2 to green and band 1 to blue
compression
number from 1 to 9. The higher the number the greater the compression.
options
text Array of GDAL
options as defined for PNG (look at create_options
for PNG of
ST_GDALDrivers
). For PNG valid one is only ZLEVEL (amount
of time to spend on compression -- default 6)
e.g. ARRAY['ZLEVEL=9'].
WORLDFILE is not allowed since the function
would have to output two outputs. Refer to
GDAL
Raster format options
for more details.
Availability: 2.0.0 - requires GDAL >= 1.6.0.
SELECT ST_AsPNG(rast) As rastpng
FROM dummy_rast WHERE rid=2;
-- export the first 3 bands and map band 3 to Red, band 1 to Green, band 2 to blue
SELECT ST_AsPNG(rast, ARRAY[3,1,2]) As rastpng
FROM dummy_rast WHERE rid=2;