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add threshold on the number of deleted vertices #19

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add threshold on the number of deleted vertices #19

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26 changes: 18 additions & 8 deletions simplify_algorithm.py
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Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@
from qgis.core import (QgsProcessing, QgsProcessingAlgorithm, QgsProcessingParameterDistance,
QgsProcessingParameterFeatureSource, QgsProcessingParameterFeatureSink,
QgsFeatureSink, QgsFeatureRequest, QgsLineString, QgsWkbTypes, QgsGeometry,
QgsProcessingException)
QgsProcessingException,QgsProcessingParameterNumber)
import processing
from .geo_sim_util import Epsilon, GsCollection, GeoSimUtil, GsFeature, ProgressBar

Expand Down Expand Up @@ -120,6 +120,12 @@ def initAlgorithm(self, config=None): # pylint: disable=unused-argument
self.tr('Diameter tolerance'),
defaultValue=0.0,
parentParameterName='INPUT')) # Make distance units match the INPUT layer units

# vertices 'Threshold' under which the iterations stop
self.addParameter(QgsProcessingParameterNumber(
'VERTICES',
self.tr('Vertices threshold'),
defaultValue=0))

# 'OUTPUT' for the results
self.addParameter(QgsProcessingParameterFeatureSink(
Expand All @@ -135,6 +141,7 @@ def processAlgorithm(self, parameters, context, feedback):
# Extract parameter
source_in = self.parameterAsSource(parameters, "INPUT", context)
tolerance = self.parameterAsDouble(parameters, "TOLERANCE", context)
threshold = self.parameterAsInt(parameters, "VERTICES", context)
validate_structure = self.parameterAsBool(parameters, "VALIDATE_STRUCTURE", context)

if source_in is None:
Expand Down Expand Up @@ -163,7 +170,7 @@ def processAlgorithm(self, parameters, context, feedback):
feedback.setProgress(1)

# Call ReduceBend algorithm
rb_return = Simplify.douglas_peucker(qgs_features_in, tolerance, validate_structure, feedback)
rb_return = Simplify.douglas_peucker(qgs_features_in, tolerance, threshold, validate_structure, feedback)

for qgs_feature_out in rb_return.qgs_features_out:
sink.addFeature(qgs_feature_out, QgsFeatureSink.FastInsert)
Expand Down Expand Up @@ -260,18 +267,19 @@ def normalize_in_vector_layer(in_vector_layer, feedback):
return qgs_in_features, geom_type

@staticmethod
def douglas_peucker(qgs_in_features, tolerance, validate_structure=False, feedback=None):
def douglas_peucker(qgs_in_features, tolerance, threshold, validate_structure=False, feedback=None):
"""Main static method used to launch the simplification of the Douglas-Peucker algorithm.

:param: qgs_features: List of QgsFeatures to process.
:param: tolerance: Simplification tolerance in ground unit.
:param: threshold: number of vertices removed under which the iteration stop
:param: validate_structure: Validate internal data structure after processing (for debugging only)
:param: feedback: QgsFeedback handle for interaction with QGIS.
:return: Statistics and results object.
:rtype: RbResults
"""

dp = Simplify(qgs_in_features, tolerance, validate_structure, feedback)
dp = Simplify(qgs_in_features, tolerance, threshold, validate_structure, feedback)
results = dp.reduce()

return results
Expand Down Expand Up @@ -300,19 +308,21 @@ def find_farthest_point(qgs_points, first, last, ):

return farthest_index, farthest_dist

__slots__ = ('tolerance', 'validate_structure', 'feedback', 'rb_collection', 'eps', 'rb_results', 'rb_geoms',
__slots__ = ('tolerance', 'threshold', 'validate_structure', 'feedback', 'rb_collection', 'eps', 'rb_results', 'rb_geoms',
'gs_features')

def __init__(self, qgs_in_features, tolerance, validate_structure, feedback):
def __init__(self, qgs_in_features, tolerance, threshold, validate_structure, feedback):
"""Constructor for Simplify algorithm.

:param: qgs_in_features: List of features to process.
:param: tolerance: Float tolerance distance of the Douglas Peucker algorithm.
:param: threshold: number of vertices removed under which the iteration stop
:param: validate_structure: flag to validate internal data structure after processing (for debugging)
:param: feedback: QgsFeedback handle for interaction with QGIS.
"""

self.tolerance = tolerance
self.threshold = threshold
self.validate_structure = validate_structure
self.feedback = feedback

Expand Down Expand Up @@ -416,8 +426,8 @@ def _simplify_lines(self):

self.feedback.pushInfo("Vertice deleted: {0}".format(nbr_vertice_deleted))

# While loop breaking condition (when no vertice deleted in a loop)
if nbr_vertice_deleted == 0:
# While loop breaking condition (when number of vertices deleted in a loop smaller than threshold)
if nbr_vertice_deleted < self.threshold:
break
self.rb_results.nbr_vertice_deleted += nbr_vertice_deleted

Expand Down