Source code for safe_qgis.clipper
"""InaSAFE Disaster risk assessment tool developed by AusAid -
**ISClipper implementation.**
Contact : ole.moller.nielsen@gmail.com
.. note:: 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 2 of the License, or
(at your option) any later version.
"""
from safe.common.utilities import temp_dir
__author__ = 'tim@linfiniti.com'
__revision__ = '$Format:%H$'
__date__ = '20/01/2011'
__copyright__ = 'Copyright 2012, Australia Indonesia Facility for '
__copyright__ += 'Disaster Reduction'
import os
import sys
import tempfile
import logging
from PyQt4.QtCore import QCoreApplication, QProcess
from qgis.core import (QGis,
QgsCoordinateTransform,
QgsCoordinateReferenceSystem,
QgsRectangle,
QgsMapLayer,
QgsFeature,
QgsVectorFileWriter,
QgsGeometry)
from safe_qgis.safe_interface import (verify,
readKeywordsFromFile)
from safe_qgis.keyword_io import KeywordIO
from safe_qgis.exceptions import (InvalidParameterError,
NoFeaturesInExtentError,
CallGDALError,
InvalidProjectionError,
InvalidClipGeometryError)
LOGGER = logging.getLogger(name='InaSAFE')
[docs]def tr(theText):
"""We define a tr() alias here since the ClipperTest implementation below
is not a class and does not inherit from QObject.
.. note:: see http://tinyurl.com/pyqt-differences
Args:
theText - string to be translated
Returns:
Translated version of the given string if available, otherwise
the original string.
"""
myContext = "@default"
return QCoreApplication.translate(myContext, theText)
[docs]def clipLayer(theLayer,
theExtent,
theCellSize=None,
theExtraKeywords=None,
theExplodeFlag=True,
theHardClipFlag=False):
"""Clip a Hazard or Exposure layer to the extents provided.
.. note:: Will delegate to clipVectorLayer or clipRasterLayer as needed.
Args:
* theLayer - a valid QGIS vector or raster layer
* theExtent either: 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.
or: A QgsGeometry of type polygon. **Polygon clipping is
currently only supported for vector datasets.**
* theCellSize - cell size which the layer should be resampled to.
This argument will be ignored for vector layers and if not provided
for a raster layer, the native raster cell size will be used.
* theExtraKeywords - Optional keywords dictionary to be added to
output layer.
* theExplodeFlag - a bool specifying whether multipart features
should be 'exploded' into singleparts. **This parameter is ignored
for raster layer clipping.**
* theHardClipFlag - a bool specifying whether line and polygon features
that extend beyond the extents should be clipped such that they
are reduced in size to the part of the geometry that intersects
the extent only. Default is False. **This parameter is ignored
for raster layer clipping.**
Returns:
Path to the output clipped layer (placed in the system temp dir).
The output layer will be reprojected to EPSG:4326 if needed.
Raises:
None
"""
if theLayer.type() == QgsMapLayer.VectorLayer:
return _clipVectorLayer(theLayer,
theExtent,
theExtraKeywords=theExtraKeywords,
theExplodeFlag=theExplodeFlag,
theHardClipFlag=theHardClipFlag)
else:
try:
return _clipRasterLayer(theLayer, theExtent, theCellSize,
theExtraKeywords=theExtraKeywords)
except CallGDALError, e:
raise e
except IOError, e:
raise e
def _clipVectorLayer(theLayer,
theExtent,
theExtraKeywords=None,
theExplodeFlag=True,
theHardClipFlag=False):
"""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 either: 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.
or: A QgsGeometry of type polygon. **Polygon clipping is
currently only supported for vector datasets.**
* theExtraKeywords - any additional keywords over and above the
original keywords that should be associated with the cliplayer.
* theExplodeFlag - a bool specifying whether multipart features
should be 'exploded' into singleparts.
* theHardClipFlag - a bool specifying whether line and polygon features
that extend beyond the extents should be clipped such that they
are reduced in size to the part of the geometry that intersects
the extent only. Default is False.
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 InvalidParameterError(myMessage)
if theLayer.type() != QgsMapLayer.VectorLayer:
myMessage = tr('Expected a vector layer but received a %s.' %
str(theLayer.type()))
raise InvalidParameterError(myMessage)
#myHandle, myFilename = tempfile.mkstemp('.sqlite', 'clip_',
# temp_dir())
myHandle, myFilename = tempfile.mkstemp('.shp', 'clip_',
temp_dir())
# 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())
myAllowedClipTypes = [QGis.WKBPolygon, QGis.WKBPolygon25D]
if type(theExtent) is list:
myRect = QgsRectangle(theExtent[0], theExtent[1],
theExtent[2], theExtent[3])
myClipPolygon = QgsGeometry.fromRect(myRect)
elif (type(theExtent) is QgsGeometry and
theExtent.wkbType in myAllowedClipTypes):
myRect = theExtent.boundingBox().toRectF()
myClipPolygon = theExtent
else:
raise InvalidClipGeometryError(
tr('Clip geometry must be an extent or a single part'
'polygon based geometry.'))
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,
#'SQLite') # FIXME (Ole): This works but is far too slow
'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 write out single part features unless theExplodeFlag is False
if theExplodeFlag:
myGeometryList = explodeMultiPartGeometry(myGeometry)
else:
myGeometryList = [myGeometry]
for myPart in myGeometryList:
myPart.transform(myXForm)
if theHardClipFlag:
# Remove any dangling bits so only intersecting area is
# kept.
myPart = clipGeometry(myClipPolygon, myPart)
if myPart is None:
continue
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.'
'If hazard and exposure data doesn\'t overlap '
'at all, it is not possible to do an analysis.'
'Another possibility is that the layers do overlap '
'but because they may have different spatial '
'references, they appear to be disjoint. '
'If this is the case, try to turn on reproject '
'on-the-fly in QGIS.')
raise NoFeaturesInExtentError(myMessage)
myKeywordIO = KeywordIO()
myKeywordIO.copyKeywords(theLayer, myFilename,
theExtraKeywords=theExtraKeywords)
return myFilename # Filename of created file
[docs]def clipGeometry(theClipPolygon, theGeometry):
"""Clip a geometry (linestring or polygon) using a clip polygon.
To do this we combine the clip polygon with the input geometry which
will add nodes to the input geometry where it intersects the clip polygon.
Next we get the symmetrical difference between the input geometry and the
combined geometry.
Args:
* theClipPolygon - QgsGeometry a Polygon or Polygon25D geometry to clip
with. Multipart polygons are not supported so the client needs to
take care of that.
* theGeometry - QgsGeometry - linestring or polygon that should be
clipped.
Returns:
QgsGeometry - clipped to the region of the clip polygon.
Raises:
None
"""
# Add nodes to input geometry where it intersects with clip
myLineTypes = [QGis.WKBLineString, QGis.WKBLineString25D]
myPointTypes = [QGis.WKBPoint, QGis.WKBPoint25D]
myPolygonTypes = [QGis.WKBPolygon, QGis.WKBPolygon25D]
myType = theGeometry.wkbType()
if myType in myLineTypes:
myCombinedGeometry = theGeometry.combine(theClipPolygon)
# Gives you the lines inside the clip
mySymmetricalGeometry = theGeometry.symDifference(myCombinedGeometry)
return mySymmetricalGeometry
elif myType in myPolygonTypes:
myIntersectionGeometry = theGeometry.intersection(theClipPolygon)
return myIntersectionGeometry
elif myType in myPointTypes:
if theClipPolygon.contains(theGeometry):
return theGeometry
else:
return None
else:
return None
[docs]def explodeMultiPartGeometry(theGeom):
"""Convert a multipart geometry to a list of single parts. This method was
adapted from Carson Farmer's fTools doGeometry implementation in QGIS.
Args:
theGeom - A geometry - if it is multipart it will be exploded.
Returns:
A list of single part geometries
Raises:
None
"""
myParts = []
if theGeom.type() == QGis.Point:
if theGeom.isMultipart():
myMultiGeometry = theGeom.asMultiPoint()
for i in myMultiGeometry:
myParts.append(QgsGeometry().fromPoint(i))
else:
myParts.append(theGeom)
elif theGeom.type() == QGis.Line:
if theGeom.isMultipart():
myMultiGeometry = theGeom.asMultiPolyline()
for i in myMultiGeometry:
myParts.append(QgsGeometry().fromPolyline(i))
else:
myParts.append(theGeom)
elif theGeom.type() == QGis.Polygon:
if theGeom.isMultipart():
myMultiGeometry = theGeom.asMultiPolygon()
for i in myMultiGeometry:
myParts.append(QgsGeometry().fromPolygon(i))
else:
myParts.append(theGeom)
return myParts
def _clipRasterLayer(theLayer, theExtent, theCellSize=None,
theExtraKeywords=None):
"""Clip a Hazard or Exposure raster layer to the extents provided. The
layer must be a raster layer or an exception will be thrown.
.. note:: The extent *must* be in EPSG:4326.
The output layer will always be in WGS84/Geographic.
Args:
* theLayer - a valid QGIS raster layer in EPSG:4326
* theExtent either: 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.
or: A QgsGeometry of type polygon. **Polygon clipping is
currently only supported for vector datasets.**
* theCellSize - cell size (in GeoCRS) which the layer should
be resampled to. If not provided for a raster layer (i.e.
theCellSize=None), the native raster cell size will be used.
Returns:
Path to the output clipped layer (placed in the
system temp dir).
Raises:
Exception if input layer is a density layer in projected coordinates -
see issue #123
"""
if not theLayer or not theExtent:
myMessage = tr('Layer or Extent passed to clip is None.')
raise InvalidParameterError(myMessage)
if theLayer.type() != QgsMapLayer.RasterLayer:
myMessage = tr('Expected a raster layer but received a %s.' %
str(theLayer.type()))
raise InvalidParameterError(myMessage)
myWorkingLayer = str(theLayer.source())
# Check for existence of keywords file
myKeywordsPath = myWorkingLayer[:-4] + '.keywords'
myMessage = tr('Input file to be clipped "%s" does not have the '
'expected keywords file %s' % (myWorkingLayer,
myKeywordsPath))
verify(os.path.isfile(myKeywordsPath), myMessage)
# Raise exception if layer is projected and refers to density (issue #123)
# FIXME (Ole): Need to deal with it - e.g. by automatically reprojecting
# the layer at this point and setting the native resolution accordingly
# in its keywords.
myKeywords = readKeywordsFromFile(myKeywordsPath)
if 'datatype' in myKeywords and myKeywords['datatype'] == 'density':
if str(theLayer.crs().authid()) != 'EPSG:4326':
# This layer is not WGS84 geographic
myMessage = ('Layer %s represents density but has spatial '
'reference "%s". Density layers must be given in '
'WGS84 geographic coordinates, so please reproject '
'and try again. For more information, see issue '
'https://github.com/AIFDR/inasafe/issues/123'
% (myWorkingLayer, theLayer.crs().toProj4()))
raise InvalidProjectionError(myMessage)
# We need to provide gdalwarp with a dataset for the clip
# because unline gdal_translate, it does not take projwin.
myClipKml = extentToKml(theExtent)
# Create a filename for the clipped, resampled and reprojected layer
myHandle, myFilename = tempfile.mkstemp('.tif', 'clip_',
temp_dir())
os.close(myHandle)
os.remove(myFilename)
# If no cell size is specified, we need to run gdalwarp without
# specifying the output pixel size to ensure the raster dims
# remain consistent.
if theCellSize is None:
myCommand = ('gdalwarp -q -t_srs EPSG:4326 -r near '
'-cutline %s -crop_to_cutline -of GTiff '
'"%s" "%s"' % (myClipKml,
myWorkingLayer,
myFilename))
else:
myCommand = ('gdalwarp -q -t_srs EPSG:4326 -r near -tr %f %f '
'-cutline %s -crop_to_cutline -of GTiff '
'"%s" "%s"' % (theCellSize,
theCellSize,
myClipKml,
myWorkingLayer,
myFilename))
myExecutablePrefix = ''
if sys.platform == 'darwin': # Mac OS X
# .. todo:: FIXME - softcode gdal version in this path
myExecutablePrefix = ('/Library/Frameworks/GDAL.framework/'
'Versions/1.9/Programs/')
myCommand = myExecutablePrefix + myCommand
LOGGER.debug(myCommand)
myResult = QProcess().execute(myCommand)
# For QProcess exit codes see
# http://qt-project.org/doc/qt-4.8/qprocess.html#execute
if myResult == -2: # cannot be started
myMessageDetail = tr('Process could not be started.')
myMessage = tr('<p>Error while executing the following shell command:'
'</p><pre>%s</pre><p>Error message: %s'
% (myCommand, myMessageDetail))
raise CallGDALError(myMessage)
elif myResult == -1: # process crashed
myMessageDetail = tr('Process could not be started.')
myMessage = tr('<p>Error while executing the following shell command:'
'</p><pre>%s</pre><p>Error message: %s'
% (myCommand, myMessageDetail))
raise CallGDALError(myMessage)
# .. todo:: Check the result of the shell call is ok
myKeywordIO = KeywordIO()
myKeywordIO.copyKeywords(theLayer, myFilename,
theExtraKeywords=theExtraKeywords)
return myFilename # Filename of created file
[docs]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>
<Placemark>
<Polygon>
<outerBoundaryIs>
<LinearRing>
<coordinates>
%s %s %s %s %s
</coordinates>
</LinearRing>
</outerBoundaryIs>
</Polygon>
</Placemark>
</Folder>
</Document>
</kml>""" %
(myBottomLeftCorner,
myTopLeftCorner,
myTopRightCorner,
myBottomRightCorner,
myBottomLeftCorner))
myFilename = tempfile.mkstemp('.kml', 'extent_',
temp_dir())[1]
myFile = file(myFilename, 'wt')
myFile.write(myKml)
myFile.close()
return myFilename
[docs]def extentToGeoArray(theExtent, theSourceCrs):
"""Convert the supplied extent to geographic and return as as array.
Args:
theExtent: QgsRectangle to be transformed to geocrs.
theSourceCrs: QgsCoordinateReferenceSystem representing the original
extent's CRS.
Returns:
list: Transformed extents in EPSG:4326 in the form
[xmin, ymin, xmix, ymax]
Raises:
None
"""
myGeoCrs = QgsCoordinateReferenceSystem()
myGeoCrs.createFromEpsg(4326)
myXForm = QgsCoordinateTransform(
theSourceCrs,
myGeoCrs)
# Get the clip area in the layer's crs
myTransformedExtent = myXForm.transformBoundingBox(theExtent)
myGeoExtent = [myTransformedExtent.xMinimum(),
myTransformedExtent.yMinimum(),
myTransformedExtent.xMaximum(),
myTransformedExtent.yMaximum()]
return myGeoExtent
