[processing] Add smooth algorithm

Allows for smoothing line or polygon layers

Author: nyalldawson

python/plugins/processing/algs/qgis/QGISAlgorithmProvider.py

@@ -131,6 +131,7 @@
 from Datasources2Vrt import Datasources2Vrt
 from CheckValidity import CheckValidity
 from OrientedMinimumBoundingBox import OrientedMinimumBoundingBox
+from Smooth import Smooth
 
 pluginPath = os.path.normpath(os.path.join(
     os.path.split(os.path.dirname(__file__))[0], os.pardir))
@@ -179,7 +180,7 @@ def __init__(self):
                         SelectByExpression(), HypsometricCurves(),
                         SplitLinesWithLines(), CreateConstantRaster(),
                         FieldsMapper(), SelectByAttributeSum(), Datasources2Vrt(),
-                        CheckValidity(), OrientedMinimumBoundingBox()
+                        CheckValidity(), OrientedMinimumBoundingBox(), Smooth()
                         ]
 
         if hasMatplotlib:

python/plugins/processing/algs/qgis/Smooth.py

@@ -0,0 +1,89 @@
+# -*- coding: utf-8 -*-
+
+"""
+***************************************************************************
+    Smooth.py
+    ---------
+    Date                 : November 2015
+    Copyright            : (C) 2015 by Nyall Dawson
+    Email                : nyall dot dawson at gmail dot com
+***************************************************************************
+*                                                                         *
+*   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.                                   *
+*                                                                         *
+***************************************************************************
+"""
+
+__author__ = 'Nyall Dawson'
+__date__ = 'November 2015'
+__copyright__ = '(C) 2015, Nyall Dawson'
+
+# This will get replaced with a git SHA1 when you do a git archive323
+
+__revision__ = '$Format:%H$'
+
+from qgis.core import QGis, QgsGeometry, QgsFeature
+from processing.core.GeoAlgorithm import GeoAlgorithm
+from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
+from processing.core.parameters import ParameterVector, ParameterNumber
+from processing.core.outputs import OutputVector
+from processing.tools import dataobjects, vector
+
+
+class Smooth(GeoAlgorithm):
+
+    INPUT_LAYER = 'INPUT_LAYER'
+    OUTPUT_LAYER = 'OUTPUT_LAYER'
+    ITERATIONS = 'ITERATIONS'
+    OFFSET = 'OFFSET'
+
+    def defineCharacteristics(self):
+        self.name, self.i18n_name = self.trAlgorithm('Smooth geometry')
+        self.group, self.i18n_group = self.trAlgorithm('Vector geometry tools')
+
+        self.addParameter(ParameterVector(self.INPUT_LAYER,
+                                          self.tr('Input layer'), [ParameterVector.VECTOR_TYPE_POLYGON, ParameterVector.VECTOR_TYPE_LINE]))
+        self.addParameter(ParameterNumber(self.ITERATIONS,
+                                          self.tr('Iterations'), default=1, minValue=1, maxValue=10))
+        self.addParameter(ParameterNumber(self.OFFSET,
+                                          self.tr('Offset'), default=0.25, minValue=0.0, maxValue=0.5))
+        self.addOutput(OutputVector(self.OUTPUT_LAYER, self.tr('Smoothed')))
+
+    def processAlgorithm(self, progress):
+        layer = dataobjects.getObjectFromUri(
+            self.getParameterValue(self.INPUT_LAYER))
+        provider = layer.dataProvider()
+        iterations = self.getParameterValue(self.ITERATIONS)
+        offset = self.getParameterValue(self.OFFSET)
+
+        writer = self.getOutputFromName(
+            self.OUTPUT_LAYER).getVectorWriter(
+                layer.fields().toList(),
+                provider.geometryType(),
+                layer.crs())
+
+        outFeat = QgsFeature()
+
+        features = vector.features(layer)
+        total = 100.0 / float(len(features))
+        current = 0
+
+        for inFeat in features:
+            inGeom = inFeat.constGeometry()
+            attrs = inFeat.attributes()
+
+            outGeom = inGeom.smooth(iterations, offset)
+            if outGeom is None:
+                raise GeoAlgorithmExecutionException(
+                    self.tr('Error smoothing geometry'))
+
+            outFeat.setGeometry(outGeom)
+            outFeat.setAttributes(attrs)
+            writer.addFeature(outFeat)
+            current += 1
+            progress.setPercentage(int(current * total))
+
+        del writer