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Better clip for very separate features

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nyalldawson committed Aug 3, 2016
1 parent 71ebdb8 commit d1aa03a09b5b7c0db953e41192ef91d25ff664da
Showing with 65 additions and 47 deletions.
  1. +65 −47 python/plugins/processing/algs/qgis/Clip.py
@@ -60,70 +60,88 @@ def defineCharacteristics(self):
self.addOutput(OutputVector(Clip.OUTPUT, self.tr('Clipped')))

def processAlgorithm(self, progress):
sourceLayer = dataobjects.getObjectFromUri(
source_layer = dataobjects.getObjectFromUri(
self.getParameterValue(Clip.INPUT))
maskLayer = dataobjects.getObjectFromUri(
mask_layer = dataobjects.getObjectFromUri(
self.getParameterValue(Clip.OVERLAY))

writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(
sourceLayer.pendingFields(),
sourceLayer.dataProvider().geometryType(),
sourceLayer.dataProvider().crs())

inFeatA = QgsFeature()
inFeatB = QgsFeature()
outFeat = QgsFeature()
source_layer.fields(),
source_layer.dataProvider().geometryType(),
source_layer.crs())

# first build up a list of clip geometries
clip_geoms = []
for maskFeat in vector.features(maskLayer, QgsFeatureRequest().setSubsetOfAttributes([])):
for maskFeat in vector.features(mask_layer, QgsFeatureRequest().setSubsetOfAttributes([])):
clip_geoms.append(maskFeat.geometry())

# are we clipping against a single feature? if so, we can show finer progress reports
if len(clip_geoms) > 1:
combined_clip_geom = QgsGeometry.unaryUnion(clip_geoms)
single_clip_feature = False
else:
combined_clip_geom = clip_geoms[0]
single_clip_feature = True

# use prepared geometries for faster insection tests
# use prepared geometries for faster intersection tests
engine = QgsGeometry.createGeometryEngine(combined_clip_geom.geometry())
engine.prepareGeometry()

input_features = [f for f in vector.features(sourceLayer, QgsFeatureRequest().setFilterRect(combined_clip_geom.boundingBox()))]
total = 100.0 / len(input_features)
for current, in_feat in enumerate(input_features):
if not in_feat.geometry():
continue

if not engine.intersects(in_feat.geometry().geometry()):
continue

if not engine.contains(in_feat.geometry().geometry()):
cur_geom = in_feat.geometry()
new_geom = combined_clip_geom.intersection(cur_geom)
if new_geom.wkbType() == Qgis.WKBUnknown or QgsWKBTypes.flatType(new_geom.geometry().wkbType()) == QgsWKBTypes.GeometryCollection:
int_com = in_feat.geometry().combine(new_geom)
int_sym = in_feat.geometry().symDifference(new_geom)
new_geom = int_com.difference(int_sym)
if new_geom.isGeosEmpty() or not new_geom.isGeosValid():
ProcessingLog.addToLog(ProcessingLog.LOG_ERROR,
self.tr('GEOS geoprocessing error: One or more '
'input features have invalid geometry.'))
tested_feature_ids = set()

for i, clip_geom in enumerate(clip_geoms):
input_features = [f for f in vector.features(source_layer, QgsFeatureRequest().setFilterRect(clip_geom.boundingBox()))]

if single_clip_feature:
total = 100.0 / len(input_features)
else:
# clip geometry totally contains feature geometry, so no need to perform intersection
new_geom = in_feat.geometry()

try:
outFeat = QgsFeature()
outFeat.setGeometry(new_geom)
outFeat.setAttributes(in_feat.attributes())
writer.addFeature(outFeat)
except:
ProcessingLog.addToLog(ProcessingLog.LOG_ERROR,
self.tr('Feature geometry error: One or more '
'output features ignored due to '
'invalid geometry.'))
continue

progress.setPercentage(int(current * total))
total = 0

for current, in_feat in enumerate(input_features):
if not in_feat.geometry():
continue

if in_feat.id() in tested_feature_ids:
# don't retest a feature we have already checked
continue

tested_feature_ids.add(in_feat.id())

if not engine.intersects(in_feat.geometry().geometry()):
continue

if not engine.contains(in_feat.geometry().geometry()):
cur_geom = in_feat.geometry()
new_geom = combined_clip_geom.intersection(cur_geom)
if new_geom.wkbType() == Qgis.WKBUnknown or QgsWKBTypes.flatType(new_geom.geometry().wkbType()) == QgsWKBTypes.GeometryCollection:
int_com = in_feat.geometry().combine(new_geom)
int_sym = in_feat.geometry().symDifference(new_geom)
new_geom = int_com.difference(int_sym)
if new_geom.isGeosEmpty() or not new_geom.isGeosValid():
ProcessingLog.addToLog(ProcessingLog.LOG_ERROR,
self.tr('GEOS geoprocessing error: One or more '
'input features have invalid geometry.'))
else:
# clip geometry totally contains feature geometry, so no need to perform intersection
new_geom = in_feat.geometry()

try:
out_feat = QgsFeature()
out_feat.setGeometry(new_geom)
out_feat.setAttributes(in_feat.attributes())
writer.addFeature(out_feat)
except:
ProcessingLog.addToLog(ProcessingLog.LOG_ERROR,
self.tr('Feature geometry error: One or more '
'output features ignored due to '
'invalid geometry.'))
continue

if single_clip_feature:
progress.setPercentage(int(current * total))

if not single_clip_feature:
# coarse progress report for multiple clip geometries
progress.setPercentage(100.0 * i / len(clip_geoms))

del writer

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