wmsimage()

gistfile1.py

    def wmsimage(self, server='http://www.gebco.net/data_and_products/gebco_web_services/web_map_service/mapserv',\
                 request='GetMap',layers='GEBCO_08_Grid',version='1.1.1',\
                 fmt='image/png',bgcolor='0xFFFFFF',transparent='TRUE',\
                 xpixels=400,ypixels=None,verbose=False,**kwargs):
        """
        Retrieve an image using the WMS server request and display it on
        the map. In order to use this method, the Basemap instance must be
        created using the ``epsg`` keyword to define the map projection, unless
        the ``cyl`` projection is used (in which case the epsg code 4326 is
        assumed).

        .. tabularcolumns:: |l|L|

        ==============   ====================================================
        Keywords         Description
        ==============   ====================================================
        server           WMS server base URL (default
                         http://server.arcgisonline.com/ArcGIS).
        request          service request (default GetMap).
        layers           comma separated list of layers.
        version          WMS server version (default 1.1.1)
        fmt              response format (default 'image/png')
        xpixels          requested number of image pixels in x-direction
                         (default 400).
        ypixels          requested number of image pixels in y-direction.
                         Default (None) is to infer the number from
                         from xpixels and the aspect ratio of the
                         map projection region.
        verbose          if True, print URL used to retrieve image (default
                         False).
        \**kwargs        extra keyword arguments passed on to
                         :meth:`imshow`
        ==============   ====================================================

        Extra keyword ``ax`` can be used to override the default axis instance.

        returns a matplotlib.image.AxesImage instance.
        """
        import urllib2
        if not hasattr(self,'epsg'):
            msg = dedent("""
            Basemap instance must be creating using an EPSG code
            (http://spatialreference.org) in order to use the wmsmap method""")
            raise ValueError(msg)
        # find the x,y values at the corner points.
        p = pyproj.Proj(init="epsg:%s" % self.epsg, preserve_units=True)
        xmin,ymin = p(self.llcrnrlon,self.llcrnrlat)
        xmax,ymax = p(self.urcrnrlon,self.urcrnrlat)
        if self.projection in _cylproj:
            Dateline =\
            _geoslib.Point(self(180.,0.5*(self.llcrnrlat+self.urcrnrlat)))
            hasDateline = Dateline.within(self._boundarypolyxy)
            if hasDateline:
                msg=dedent("""
                wmsimage cannot handle images that cross
                the dateline for cylindrical projections.""")
                raise ValueError(msg)
        if self.projection == 'cyl':
            xmin = (180./np.pi)*xmin; xmax = (180./np.pi)*xmax
            ymin = (180./np.pi)*ymin; ymax = (180./np.pi)*ymax
        # ypixels not given, find by scaling xpixels by the map aspect ratio.
        if ypixels is None:
            ypixels = int(self.aspect*xpixels)

        #~ GetCapabilities and do raw validation on requested parameters:
        import xml.etree.ElementTree as ET
        try:
            msg = ''
            doc = ET.parse(urllib2.urlopen(server + "?SERVICE=WMS&REQUEST=GetCapabilities"))
            #~ Check if requested format is supported by WMS server:
            for node in doc.findall('.//Capability/Request/GetMap/Format'):
                msg = msg + node.text + '\n'
                if fmt == node.text:
                    msg = False
                    break
            if msg:
                raise ValueError('Format "%s" is not supported.\nServer supports following formats:\n%s' \
                    % (fmt, msg))
            #~ Check version and projection parameter
            sr = 'SRS'; msg = ''
            v = doc.getroot().get('version')
            if not version == v:
                print 'Server reports WMS version: "%s" while request is made for version %s' \
                    % (v, version)
            if len(v) == 5 and int(v.replace('.','')) > 111:
                sr = 'CRS'
            #~ Check supported projections
            for node in doc.findall('.//Capability/Layer/' + sr):
                node = node.text.replace(',', '')
                msg = msg + node + '\n'
                if 'EPSG:' + str(self.epsg) == node:
                    msg = False
                    break
            if msg:
                raise ValueError('Projection "EPSG:%s" is not supported.\nServer support following projections:\n%s' \
                    % (str(self.epsg), msg))
        except:
            raise ValueError('Problem getting WMS capabilities.\nProbably wrong server address or server out of order')

        # construct a WMS URL request.
        basemap_url = \
"%s?service=WMS&version=%s&request=%s&layers=%s&\
bbox=%d,%d,%d,%d&\
%s=EPSG:%s&\
format=%s&\
bgcolor=%s&\
transparent=%s&\
width=%s&\
height=%s" %\
(server,version,request,layers,xmin,ymin,xmax,ymax,sr,self.epsg,fmt,bgcolor,transparent,xpixels,ypixels)

        # print URL?
        if verbose: print basemap_url

        #~ WMS servers seem to transfer chunked response, which imread() can't
        #~ handle transparently.
        #~ Transfer encoding is checked and `cStringIO` module is engaged:
        resp = urllib2.urlopen(basemap_url)
        if resp.headers['content-type'] == fmt:
            if resp.headers['transfer-encoding'] == 'chunked':
                import cStringIO
                sio_img = cStringIO.StringIO()
                while True:
                    chunk = resp.read()
                    if not chunk:
                        break
                    sio_img.write(chunk)
                sio_img.seek(0)
                wms_img = imread(sio_img)
                sio_img.close()
            else:
                wms_img = imread(resp)
            resp.close()
            return self.imshow(wms_img, origin='upper', **kwargs)
        elif resp.headers['content-type'] == 'application/vnd.ogc.se_xml':
            raise ValueError(ET.parse(resp).find('.//ServiceException').text)
        else:
            raise ValueError('Unknown error occured, please re-check parameters')