Source Code for Module madrona.xyquery.views

 1  import struct 
 2  from osgeo import gdal 
 3  from django.shortcuts import render_to_response 
 4  from django.contrib.gis.geos import Point as GEOSPoint 
 5  from django.contrib.gis.gdal import SpatialReference 
 6  from models import Attribute, Feature, Raster 
 7   
 8   
 9 -def query(request): 
10      x = float(request.REQUEST['x']) 
11      y = float(request.REQUEST['y']) 
12      pnt = GEOSPoint(x,y,srid=4326) 
13   
14      # Query all the vector polygon layers 
15      polygons = Feature.objects.filter(geom__bboverlaps=pnt).filter(geom__intersects=pnt) 
16      results = {} 
17      for poly in polygons: 
18          attribs = Attribute.objects.filter(feature=poly.pk) 
19          for attrib in attribs: 
20              results['%s :: %s' % (poly.layer, attrib.key)] = attrib.value 
21   
22      # Query all the raster layers 
23      rasters = Raster.objects.all() 
24      for rast in rasters: 
25          ds = gdal.Open(str(rast.filepath)) 
26          numbands = ds.RasterCount 
27          srs = SpatialReference(ds.GetProjection()) 
28          pnt_proj = pnt.transform(srs,clone=True) 
29          for band in range(1,numbands + 1): 
30              val = getRasterValue(pnt_proj.x, pnt_proj.y, ds, band) 
31              if val: 
32                  results["%s :: %s" % (rast.layer, "Band %s" % band)] = val 
33   
34      return render_to_response('query.html', {'x': x, 'y':y, 'results': results})  
35   
36 -def getRasterValue(x,y,ds,bandnum=1): 
37      band = ds.GetRasterBand(bandnum) 
38      gt = ds.GetGeoTransform() 
39      nodata = band.GetNoDataValue() 
40      try: 
41          xoff = int((x - gt[0]) / gt[1]) 
42          yoff = int((y - gt[3]) / gt[5])  
43          a = band.ReadAsArray(xoff, yoff, 1, 1) 
44          #return float(Numeric.sum( Numeric.sum(a) ) / Numeric.size(a)) 
45          val = a[0][0] 
46          if val == nodata: 
47              return None 
48          else: 
49              return val 
50      except: 
51          return None 
52