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Optimise calculation of envelopes for MinimumBoundingGeometry alg 
It's more efficient to calculate these on the fly, rather then
collecting all geometry points and then calculating.
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@nyalldawson
nyalldawson committed Sep 3, 2017
1 parent 83affdc commit b6e3542
Showing 1 changed file with 64 additions and 23 deletions.
87 python/plugins/processing/algs/qgis/MinimumBoundingGeometry.py
View file
@@ -38,6 +38,7 @@
QgsWkbTypes,
QgsFeatureRequest,
QgsFields,
QgsRectangle,
QgsProcessingParameterFeatureSource,
QgsProcessingParameterField,
QgsProcessingParameterEnum,
@@ -53,7 +54,6 @@


class MinimumBoundingGeometry(QgisAlgorithm):

INPUT = 'INPUT'
OUTPUT = 'OUTPUT'
TYPE = 'TYPE'
@@ -76,11 +76,13 @@ def initAlgorithm(self, config=None):
self.addParameter(QgsProcessingParameterFeatureSource(self.INPUT,
self.tr('Input layer')))
self.addParameter(QgsProcessingParameterField(self.FIELD,
self.tr('Field (optional, set if features should be grouped by class)'),
self.tr(
'Field (optional, set if features should be grouped by class)'),
parentLayerParameterName=self.INPUT, optional=True))
self.addParameter(QgsProcessingParameterEnum(self.TYPE,
self.tr('Geometry type'), options=self.type_names))
self.addParameter(QgsProcessingParameterFeatureSink(self.OUTPUT, self.tr('Bounding geometry'), QgsProcessing.TypeVectorPolygon))
self.addParameter(QgsProcessingParameterFeatureSink(self.OUTPUT, self.tr('Bounding geometry'),
QgsProcessing.TypeVectorPolygon))

def name(self):
return 'minimumboundinggeometry'
@@ -89,7 +91,9 @@ def displayName(self):
return self.tr('Minimum bounding geometry')

def tags(self):
return self.tr('bounding,box,bounds,envelope,minimum,oriented,rectangle,enclosing,circle,convex,hull,generalization').split(',')
return self.tr(
'bounding,box,bounds,envelope,minimum,oriented,rectangle,enclosing,circle,convex,hull,generalization').split(
',')

def processAlgorithm(self, parameters, context, feedback):
source = self.parameterAsSource(parameters, self.INPUT, context)
@@ -108,13 +112,13 @@ def processAlgorithm(self, parameters, context, feedback):
if field_index >= 0:
fields.append(source.fields()[field_index])
if type == 0:
#envelope
# envelope
fields.append(QgsField('width', QVariant.Double, '', 20, 6))
fields.append(QgsField('height', QVariant.Double, '', 20, 6))
fields.append(QgsField('area', QVariant.Double, '', 20, 6))
fields.append(QgsField('perimeter', QVariant.Double, '', 20, 6))
elif type == 1:
#oriented rect
# oriented rect
fields.append(QgsField('width', QVariant.Double, '', 20, 6))
fields.append(QgsField('height', QVariant.Double, '', 20, 6))
fields.append(QgsField('angle', QVariant.Double, '', 20, 6))
@@ -134,6 +138,7 @@ def processAlgorithm(self, parameters, context, feedback):

if field_index >= 0:
geometry_dict = {}
bounds_dict = {}
total = 50.0 / source.featureCount() if source.featureCount() else 1
features = source.getFeatures(QgsFeatureRequest().setSubsetOfAttributes([field_index]))
for current, f in enumerate(features):
@@ -143,41 +148,77 @@ def processAlgorithm(self, parameters, context, feedback):
if not f.hasGeometry():
continue

if not f.attributes()[field_index] in geometry_dict:
geometry_dict[f.attributes()[field_index]] = [f.geometry()]
if type == 0:
# bounding boxes - calculate on the fly for efficiency
if not f.attributes()[field_index] in bounds_dict:
bounds_dict[f.attributes()[field_index]] = f.geometry().boundingBox()
else:
bounds_dict[f.attributes()[field_index]].combineExtentWith(f.geometry().boundingBox())
else:
geometry_dict[f.attributes()[field_index]].append(f.geometry())
if not f.attributes()[field_index] in geometry_dict:
geometry_dict[f.attributes()[field_index]] = [f.geometry()]
else:
geometry_dict[f.attributes()[field_index]].append(f.geometry())

feedback.setProgress(int(current * total))

current = 0
total = 50.0 / len(geometry_dict) if geometry_dict else 1
for group, geometries in geometry_dict.items():
if feedback.isCanceled():
break

feature = self.createFeature(feedback, current, type, geometries, group)
sink.addFeature(feature, QgsFeatureSink.FastInsert)
geometry_dict[group] = None

feedback.setProgress(50 + int(current * total))
current += 1
if type == 0:
# bounding boxes
current = 0
total = 50.0 / len(bounds_dict) if bounds_dict else 1
for group, rect in bounds_dict.items():
if feedback.isCanceled():
break

# envelope
feature = QgsFeature()
feature.setGeometry(QgsGeometry.fromRect(rect))
feature.setAttributes([current, group, rect.width(), rect.height(), rect.area(), rect.perimeter()])
sink.addFeature(feature, QgsFeatureSink.FastInsert)
geometry_dict[group] = None

feedback.setProgress(50 + int(current * total))
current += 1
else:
current = 0
total = 50.0 / len(geometry_dict) if geometry_dict else 1

for group, geometries in geometry_dict.items():
if feedback.isCanceled():
break

feature = self.createFeature(feedback, current, type, geometries, group)
sink.addFeature(feature, QgsFeatureSink.FastInsert)
geometry_dict[group] = None

feedback.setProgress(50 + int(current * total))
current += 1
else:
total = 80.0 / source.featureCount() if source.featureCount() else 1
features = source.getFeatures(QgsFeatureRequest().setSubsetOfAttributes([]))
geometry_queue = []
bounds = QgsRectangle()
for current, f in enumerate(features):
if feedback.isCanceled():
break

if not f.hasGeometry():
continue

geometry_queue.append(f.geometry())
if type == 0:
# bounding boxes, calculate on the fly for efficiency
bounds.combineExtentWith(f.geometry().boundingBox())
else:
geometry_queue.append(f.geometry())
feedback.setProgress(int(current * total))

if not feedback.isCanceled():
feature = self.createFeature(feedback, 0, type, geometry_queue)
if type == 0:
feature = QgsFeature()
feature.setGeometry(QgsGeometry.fromRect(bounds))
feature.setAttributes([0, bounds.width(), bounds.height(), bounds.area(), bounds.perimeter()])
else:
feature = self.createFeature(feedback, 0, type, geometry_queue)
sink.addFeature(feature, QgsFeatureSink.FastInsert)

return {self.OUTPUT: dest_id}

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