PostGIS
Name
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.
Synopsis
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`)`;
Description
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:
-
nbandis for single band exports. -
nbandsis 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 -
compressionnumber from 1 to 9. The higher the number the greater the compression. -
optionstext 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.
Examples
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;See Also
ST_AsGDALRaster, ST_ColorMap, ST_GDALDrivers, Section 9.3, “Building Custom Applications with PostGIS Raster”
ST_AsJPEG |
ST_AsTIFF |