def _clipVectorLayer(theLayer, theExtent,
theExtraKeywords=None):
"""Clip a Hazard or Exposure layer to the
extents of the current view frame. The layer must be a
vector layer or an exception will be thrown.
The output layer will always be in WGS84/Geographic.
Args:
* theLayer - a valid QGIS vector layer in EPSG:4326
* theExtent - an array representing the exposure layer
extents in the form [xmin, ymin, xmax, ymax]. It is assumed
that the coordinates are in EPSG:4326 although currently
no checks are made to enforce this.
* theExtraKeywords - any additional keywords over and above the
original keywords that should be associated with the cliplayer.
Returns:
Path to the output clipped layer (placed in the
system temp dir).
Raises:
None
"""
if not theLayer or not theExtent:
myMessage = tr('Layer or Extent passed to clip is None.')
raise InvalidParameterException(myMessage)
if theLayer.type() != QgsMapLayer.VectorLayer:
myMessage = tr('Expected a vector layer but received a %s.' %
str(theLayer.type()))
raise InvalidParameterException(myMessage)
myHandle, myFilename = tempfile.mkstemp('.shp', 'clip_',
getTempDir())
# Ensure the file is deleted before we try to write to it
# fixes windows specific issue where you get a message like this
# ERROR 1: c:\temp\inasafe\clip_jpxjnt.shp is not a directory.
# This is because mkstemp creates the file handle and leaves
# the file open.
os.close(myHandle)
os.remove(myFilename)
# Get the clip extents in the layer's native CRS
myGeoCrs = QgsCoordinateReferenceSystem()
myGeoCrs.createFromId(4326, QgsCoordinateReferenceSystem.EpsgCrsId)
myXForm = QgsCoordinateTransform(myGeoCrs, theLayer.crs())
myRect = QgsRectangle(theExtent[0], theExtent[1],
theExtent[2], theExtent[3])
myProjectedExtent = myXForm.transformBoundingBox(myRect)
# Get vector layer
myProvider = theLayer.dataProvider()
if myProvider is None:
myMessage = tr('Could not obtain data provider from '
'layer "%s"' % theLayer.source())
raise Exception(myMessage)
# get the layer field list, select by our extent then write to disk
# .. todo:: FIXME - for different geometry types we should implement
# different clipping behaviour e.g. reject polygons that
# intersect the edge of the bbox. Tim
myAttributes = myProvider.attributeIndexes()
myFetchGeometryFlag = True
myUseIntersectFlag = True
myProvider.select(myAttributes,
myProjectedExtent,
myFetchGeometryFlag,
myUseIntersectFlag)
myFieldList = myProvider.fields()
myWriter = QgsVectorFileWriter(myFilename,
'UTF-8',
myFieldList,
theLayer.wkbType(),
myGeoCrs,
'ESRI Shapefile')
if myWriter.hasError() != QgsVectorFileWriter.NoError:
myMessage = tr('Error when creating shapefile: <br>Filename:'
'%s<br>Error: %s' %
(myFilename, myWriter.hasError()))
raise Exception(myMessage)
# Reverse the coordinate xform now so that we can convert
# geometries from layer crs to geocrs.
myXForm = QgsCoordinateTransform(theLayer.crs(), myGeoCrs)
# Retrieve every feature with its geometry and attributes
myFeature = QgsFeature()
myCount = 0
while myProvider.nextFeature(myFeature):
myGeometry = myFeature.geometry()
# Loop through the parts adding them to the output file
# we ALWAYS write out single part features
myGeometryList = explodeMultiPartGeometry(myGeometry)
for myPart in myGeometryList:
myPart.transform(myXForm)
myFeature.setGeometry(myPart)
myWriter.addFeature(myFeature)
myCount += 1
del myWriter # Flush to disk
if myCount < 1:
myMessage = tr('No features fall within the clip extents. '
'Try panning / zooming to an area containing data '
'and then try to run your analysis again.')
raise NoFeaturesInExtentException(myMessage)
myKeywordIO = ISKeywordIO()
myKeywordIO.copyKeywords(theLayer, myFilename,
theExtraKeywords=theExtraKeywords)
return myFilename # Filename of created file
myMessage = tr('<p>Error while executing the following shell command:'
'</p><pre>%s</pre><p>Error message: %s'
% (myCommand, str(e)))
# shameless hack - see https://github.com/AIFDR/inasafe/issues/141
if sys.platform == 'darwin': # Mac OS X
if 'Errno 4' in str(e):
# continue as the error seems to be non critical
pass
else:
raise Exception(myMessage)
else:
raise Exception(myMessage)
# .. todo:: Check the result of the shell call is ok
myKeywordIO = ISKeywordIO()
myKeywordIO.copyKeywords(theLayer, myFilename,
theExtraKeywords=theExtraKeywords)
return myFilename # Filename of created file
def extentToKml(theExtent):
"""A helper to get a little kml doc for an extent so that
we can use it with gdal warp for clipping."""
myBottomLeftCorner = '%f,%f' % (theExtent[0], theExtent[1])
myTopLeftCorner = '%f,%f' % (theExtent[0], theExtent[3])
myTopRightCorner = '%f,%f' % (theExtent[2], theExtent[3])
myBottomRightCorner = '%f,%f' % (theExtent[2], theExtent[1])
myKml = ("""<?xml version="1.0" encoding="utf-8" ?>
<kml xmlns="http://www.opengis.net/kml/2.2">
<Document>
<Folder>
