rtgdalraster.py

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#! /usr/bin/env python
#
#
# A simple utility for passing parameters to ST_AsGDALRaster
# for a GDAL raster output
# This utility is handy for debugging purposes.
#
# Example:
#   rtgdalraster.py -d "dbname=postgres" -r "(SELECT rast FROM pele LIMIT 1)" -f JPEG -o pele.jpg
#
#

from optparse import OptionParser
import sys
import os
import psycopg2

def logit(msg):
        if VERBOSE is True:
                sys.stderr.write("LOG - " + str(msg) + "\n")


try:
        prs = OptionParser(version="%prog",
                usage="%prog -d <DB> -r <RASTER> -o <FILE> [-f <FORMAT>] [-c <OPTIONS>]",
                description="Output raster in a GDAL raster format")
        prs.add_option("-d", "--db", dest="db", action="store", default=None,
                help="PostgreSQL database connection string, required")
        prs.add_option("-r", "--raster", dest="raster", action="store", default=None,
                help="sql expression to create or access a existing raster, required")
        prs.add_option("-o", "--output", dest="output", action="store", default=None,
                help="file to put the output of ST_AsGDALRaster if successful, required")
        prs.add_option("-f", "--format", dest="format", action="store", default="GTiff",
                help="format of GDAL raster output, optional, default=GTiff")
        prs.add_option("-c", "--config", dest="config", action="store", default=None,
                help="comma separated list of GDAL raster creation options, optional")
        prs.add_option("-v", "--verbose", dest="verbose", action="store_true", default=False,
                help="be excessively verbose and useful for debugging")

        (opts, args) = prs.parse_args()

        if opts.db is None:
                prs.error("use -d option to specify database connection string")
        if opts.raster is None:
                prs.error("use -r option to specify a sql expression for a raster")
        if opts.output is None:
                prs.error("use -o option to specify raster output file")

        if opts.config is not None:
                opts.cfg = opts.config.split(',')
        else:
                opts.cfg = None

        global VERBOSE
        VERBOSE = opts.verbose

        conn = psycopg2.connect(opts.db)
        logit("Connected to %s" % opts.db)
        logit("Raster expression is %s" % opts.raster)

        cur = conn.cursor()
        sql = "SELECT ST_AsGDALRaster(%s, %%s, %%s::text[], NULL::integer)" % (opts.raster)
        cur.execute(sql, (opts.format, opts.cfg))
        logit("Number of rows: %i" % cur.rowcount)
        rec = cur.fetchone()[0];
        logit("size of raster (bytes): %i" % len(rec))

        fh = open(opts.output, 'wb', -1)
        fh.write(rec);
        fh.flush();
        fh.close();
        logit("size of %s (bytes): %i" % (opts.output, os.stat(opts.output)[6]));

        cur.close();
        conn.close();

        print "raster outputted to %s" % opts.output;

except Exception, e:
    print "ERROR: ", e