downdem script

downdem.py

from processing.gui.RectangleMapTool import RectangleMapTool
from owslib.wcs import WebCoverageService
import tempfile
import os

## risoluzione DEM, i possibili valori sono: 20, 40 e 75
RES = '20'

def run():
    ms = canvas.mapSettings()
    crs = ms.destinationCrs()
    msg_bar = iface.messageBar()

    r = tool.rectangle()
    s = (r.xMinimum(), r.xMaximum(), r.yMinimum(), r.yMaximum())
    try:
        if crs.authid() != 'EPSG:4326':
            msg_bar.pushMessage("downdem script",
                                "Il sistema di riferimento del progetto deve essere WGS84.", 
                                0, 5)
            return

        dem = get_dem_from_extent(s)
        lyr = QgsRasterLayer(dem, "DEM")
        QgsMapLayerRegistry.instance().addMapLayers([lyr])

        msg_bar.pushMessage("downdem script", 
                            "DEM caricato correttamente.", 
                            3, 5)
    finally:
        tool.reset()
        canvas.setMapTool(map_tool)


def get_dem_from_extent(s):
    dirpath = tempfile.mkdtemp()
    bbox = (s[0], s[3], s[1], s[2])
    wcs_url = 'http://wms.pcn.minambiente.it/wcs/dtm_' + RES + 'm'

    w = WebCoverageService(wcs_url, version='1.0.0')
    output = w.getCoverage(identifier='EL.DTM.' + RES + 'M',
                           format='GeoTIFF',
                           bbox=bbox,
                           crs='EPSG:4326',
                           width=400, height=300)

    with open(os.path.join(dirpath, 'dem.tif'), 'wb') as f:
        f.write(output.read())
    
    return os.path.join(dirpath, 'dem.tif')


canvas = iface.mapCanvas()
map_tool = canvas.mapTool()
tool = RectangleMapTool(canvas)
tool.rectangleCreated.connect(run)
canvas.setMapTool(tool)