[postgis-commits] svn - r3857 - spike/wktraster/scripts

[postgis-commits at postgis.refractions.net]

Author: mloskot
Date: 2009-03-12 10:56:41 -0700 (Thu, 12 Mar 2009)
New Revision: 3857

Added:
   spike/wktraster/scripts/pyrtreader.py
Log:
scripts: Added a simple driver to read RASTER field data directly from a table. Tha main purpose of the RasterReader is to test and debug WKT Raster implementation. It is not supposed to be an efficient performance killer, by no means.

Added: spike/wktraster/scripts/pyrtreader.py
===================================================================
--- spike/wktraster/scripts/pyrtreader.py	2009-03-11 19:46:07 UTC (rev 3856)
+++ spike/wktraster/scripts/pyrtreader.py	2009-03-12 17:56:41 UTC (rev 3857)
@@ -0,0 +1,138 @@
+#! /usr/bin/env python
+#
+# $Id$
+#
+# A simple driver to read RASTER field data directly from PostGIS/WKTRaster.
+#
+# Copyright (C) 2009 Mateusz Loskot <mateusz at loskot.net>
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+#
+###############################################################################
+#
+# Requirements: psycopg2
+#
+# WARNING: Tha main purpose of the RasterReader is to test and debug
+# WKT Raster implementation. It is not supposed to be an efficient
+# performance killer, by no means.
+#
+###############################################################################
+import psycopg2
+import sys
+
+###############################################################################
+# RASTER driver (read-only)
+
+class RasterError(Exception):
+    def __init__(self, msg):
+        self.msg = msg 
+    def __str__(self):
+        return self.msg
+
+class RasterReader(object):
+    """Reader of RASTER data stored in specified column and row (where) in a table"""
+
+    # Constructors
+
+    def __init__(self, connstr, table, column, where = ""):
+        self._connstr = connstr 
+        self._conn = None
+        self._table = table
+        self._column = column
+        self._where = where
+        self._sizes = None
+        # Connect and read RASTER header
+        self._setup()
+
+    # Public properties
+
+    db = property(fget = lambda self: self._get_db())
+    table = property(fget = lambda self: self._get_table())
+    column = property(fget = lambda self: self._get_column())
+    width = property(fget = lambda self: self._get_width())
+    height = property(fget = lambda self: self._get_height())
+    num_bands = property(fget = lambda self: self._get_num_bands())
+
+    # Public methods 
+
+    def get_value(self, band, x, y):
+        return self._query_value(band, x, y)
+
+    # Private methods 
+    
+    def _get_db(self):
+        n = filter(lambda db: db[:6] == 'dbname', self._connstr.split())[0].split('=')[1]
+        return n.strip('\'').strip()
+
+    def _get_table(self):
+        return self._table
+
+    def _get_column(self):
+        return self._column
+
+    def _get_width(self):
+        return self._query_raster_size(0)
+
+    def _get_height(self):
+        return self._query_raster_size(1)
+
+    def _get_num_bands(self):
+        return self._query_raster_size(2)
+
+    def _setup(self):
+        self._connect()
+
+    def _connect(self):
+        try:
+            if self._conn is None:
+                self._conn = psycopg2.connect(self._connstr)
+        except:
+            raise RasterError("Falied to connect to %s" % self._connstr)
+
+    def _query_single_row(self, sql):
+        assert self._conn is not None
+        try:
+            cur = self._conn.cursor()
+            cur.execute(sql)
+        except:
+            raise RasterError("Falied to execute query: %s" % sql)
+
+        row = cur.fetchone()
+        if row is None:
+            raise RasterError("No tupes returned for query: %s" % sql)
+        return row
+
+    def _query_value(self, band, x, y):
+        sql = """SELECT rt_value(%s, %d, %d, %d) FROM %s""" % \
+                 (self._column, band, x, y, self._table)
+        if len(self._where) > 0:
+            sql += """ WHERE %s""" % self._where
+        row = self._query_single_row(sql)
+        if row is None:
+            raise RasterError("Value of pixel %dx%d of band %d is none" %(x, y, band))
+        return row[0]
+    
+    def _query_raster_size(self, dim, force = False):
+        if self._sizes is None or force is True:
+            sql = """SELECT rt_width(%s), rt_height(%s), rt_numbands(%s) FROM %s""" % \
+                     (self._column, self._column, self._column, self._table)
+            if len(self._where) > 0:
+                sql += """ WHERE %s""" % self._where
+            self._sizes = self._query_single_row(sql)
+
+        if self._sizes is None:
+            raise RasterError("Falied to query %dx%d of band %d is none" %(x, y, band))
+        return self._sizes[dim]
+