Port a multi-step algorithm to new API (concave hull)

Author: nyalldawson

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

@@ -32,14 +32,16 @@
                        QgsFeatureSink,
                        QgsWkbTypes,
                        QgsApplication,
-                       QgsProcessingUtils)
+                       QgsProcessingUtils,
+                       QgsProcessingParameterFeatureSource,
+                       QgsProcessingParameterVectorLayer,
+                       QgsProcessingParameterDefinition,
+                       QgsProcessingParameterNumber,
+                       QgsProcessingParameterBoolean,
+                       QgsProcessingParameterFeatureSink,
+                       QgsProcessingOutputVectorLayer)
 from processing.algs.qgis.QgisAlgorithm import QgisAlgorithm
 from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
-from processing.core.parameters import ParameterVector
-from processing.core.parameters import ParameterNumber
-from processing.core.parameters import ParameterBoolean
-from processing.core.outputs import OutputVector
-from processing.tools import dataobjects
 import processing
 from math import sqrt
 
@@ -57,17 +59,19 @@ def group(self):
 
     def __init__(self):
         super().__init__()
-        self.addParameter(ParameterVector(ConcaveHull.INPUT,
-                                          self.tr('Input point layer'), [dataobjects.TYPE_VECTOR_POINT]))
-        self.addParameter(ParameterNumber(self.ALPHA,
-                                          self.tr('Threshold (0-1, where 1 is equivalent with Convex Hull)'),
-                                          0, 1, 0.3))
-        self.addParameter(ParameterBoolean(self.HOLES,
-                                           self.tr('Allow holes'), True))
-        self.addParameter(ParameterBoolean(self.NO_MULTIGEOMETRY,
-                                           self.tr('Split multipart geometry into singleparts geometries'), False))
-        self.addOutput(
-            OutputVector(ConcaveHull.OUTPUT, self.tr('Concave hull'), datatype=[dataobjects.TYPE_VECTOR_POLYGON]))
+
+        self.addParameter(QgsProcessingParameterFeatureSource(self.INPUT, self.tr('Input point layer'), [QgsProcessingParameterDefinition.TypeVectorPoint]))
+        self.addParameter(QgsProcessingParameterNumber(self.ALPHA,
+                                                       self.tr('Threshold (0-1, where 1 is equivalent with Convex Hull)'),
+                                                       minValue=0, maxValue=1, defaultValue=0.3, type=QgsProcessingParameterNumber.Double))
+
+        self.addParameter(QgsProcessingParameterBoolean(self.HOLES,
+                                                        self.tr('Allow holes'), defaultValue=True))
+        self.addParameter(QgsProcessingParameterBoolean(self.NO_MULTIGEOMETRY,
+                                                        self.tr('Split multipart geometry into singleparts geometries'), defaultValue=False))
+
+        self.addParameter(QgsProcessingParameterFeatureSink(self.OUTPUT, self.tr('Concave hull'), type=QgsProcessingParameterDefinition.TypeVectorPolygon))
+        self.addOutput(QgsProcessingOutputVectorLayer(self.OUTPUT, self.tr("Concave hull"), type=QgsProcessingParameterDefinition.TypeVectorPolygon))
 
     def name(self):
         return 'concavehull'
@@ -76,28 +80,31 @@ def displayName(self):
         return self.tr('Concave hull')
 
     def processAlgorithm(self, parameters, context, feedback):
-        layer = QgsProcessingUtils.mapLayerFromString(self.getParameterValue(ConcaveHull.INPUT), context)
-        alpha = self.getParameterValue(self.ALPHA)
-        holes = self.getParameterValue(self.HOLES)
-        no_multigeom = self.getParameterValue(self.NO_MULTIGEOMETRY)
+        layer = self.parameterAsSource(parameters, ConcaveHull.INPUT, context)
+        alpha = self.parameterAsDouble(parameters, self.ALPHA, context)
+        holes = self.parameterAsBool(parameters, self.HOLES, context)
+        no_multigeom = self.parameterAsBool(parameters, self.NO_MULTIGEOMETRY, context)
 
         # Delaunay triangulation from input point layer
         feedback.setProgressText(self.tr('Creating Delaunay triangles...'))
-        delone_triangles = processing.run("qgis:delaunaytriangulation", layer, None, context=context)['OUTPUT']
+        delone_triangles = processing.run("qgis:delaunaytriangulation", {'INPUT': parameters[ConcaveHull.INPUT], 'OUTPUT': 'memory:'}, feedback=feedback, context=context)['OUTPUT']
         delaunay_layer = QgsProcessingUtils.mapLayerFromString(delone_triangles, context)
 
         # Get max edge length from Delaunay triangles
         feedback.setProgressText(self.tr('Computing edges max length...'))
 
-        features = QgsProcessingUtils.getFeatures(delaunay_layer, context)
-        count = QgsProcessingUtils.featureCount(delaunay_layer, context)
+        features = delaunay_layer.getFeatures()
+        count = delaunay_layer.featureCount()
         if count == 0:
             raise GeoAlgorithmExecutionException(self.tr('No Delaunay triangles created.'))
 
         counter = 50. / count
         lengths = []
         edges = {}
         for feat in features:
+            if feedback.isCanceled():
+                break
+
             line = feat.geometry().asPolygon()[0]
             for i in range(len(line) - 1):
                 lengths.append(sqrt(line[i].sqrDist(line[i + 1])))
@@ -111,6 +118,9 @@ def processAlgorithm(self, parameters, context, feedback):
         i = 0
         ids = []
         for id, max_len in list(edges.items()):
+            if feedback.isCanceled():
+                break
+
             if max_len > alpha * max_length:
                 ids.append(id)
             feedback.setProgress(50 + i * counter)
@@ -124,21 +134,25 @@ def processAlgorithm(self, parameters, context, feedback):
 
         # Dissolve all Delaunay triangles
         feedback.setProgressText(self.tr('Dissolving Delaunay triangles...'))
-        dissolved = processing.run("qgis:dissolve", delaunay_layer.id(),
-                                   True, None, None, context=context)['OUTPUT']
+        dissolved = processing.run("native:dissolve", {'INPUT': delaunay_layer.id(), 'OUTPUT': 'memory:'}, feedback=feedback, context=context)['OUTPUT']
         dissolved_layer = QgsProcessingUtils.mapLayerFromString(dissolved, context)
 
         # Save result
         feedback.setProgressText(self.tr('Saving data...'))
         feat = QgsFeature()
-        QgsProcessingUtils.getFeatures(dissolved_layer, context).nextFeature(feat)
-        writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(layer.fields(), QgsWkbTypes.Polygon,
-                                                                     layer.crs(), context)
+        dissolved_layer.getFeatures().nextFeature(feat)
+
+        (sink, dest_id) = self.parameterAsSink(parameters, self.OUTPUT, context,
+                                               layer.fields(), QgsWkbTypes.Polygon, layer.sourceCrs())
+
         geom = feat.geometry()
         if no_multigeom and geom.isMultipart():
             # Only singlepart geometries are allowed
             geom_list = geom.asMultiPolygon()
             for single_geom_list in geom_list:
+                if feedback.isCanceled():
+                    break
+
                 single_feature = QgsFeature()
                 single_geom = QgsGeometry.fromPolygon(single_geom_list)
                 if not holes:
@@ -147,13 +161,14 @@ def processAlgorithm(self, parameters, context, feedback):
                     while deleted:
                         deleted = single_geom.deleteRing(1)
                 single_feature.setGeometry(single_geom)
-                writer.addFeature(single_feature, QgsFeatureSink.FastInsert)
+                sink.addFeature(single_feature, QgsFeatureSink.FastInsert)
         else:
             # Multipart geometries are allowed
             if not holes:
                 # Delete holes
                 deleted = True
                 while deleted:
                     deleted = geom.deleteRing(1)
-            writer.addFeature(feat, QgsFeatureSink.FastInsert)
-        del writer
+            sink.addFeature(feat, QgsFeatureSink.FastInsert)
+
+        return {self.OUTPUT: dest_id}

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

@@ -47,6 +47,7 @@
 from .Boundary import Boundary
 from .BoundingBox import BoundingBox
 from .CheckValidity import CheckValidity
+from .ConcaveHull import ConcaveHull
 from .CreateAttributeIndex import CreateAttributeIndex
 from .Delaunay import Delaunay
 from .DeleteColumn import DeleteColumn
@@ -110,7 +111,6 @@
 # from .HubDistanceLines import HubDistanceLines
 # from .HubLines import HubLines
 # from .GeometryConvert import GeometryConvert
-# from .ConcaveHull import ConcaveHull
 # from .RasterLayerStatistics import RasterLayerStatistics
 # from .StatisticsByCategories import StatisticsByCategories
 # from .EquivalentNumField import EquivalentNumField
@@ -206,7 +206,7 @@ def getAlgs(self):
         #          JoinAttributes(),
         #         Explode(), FieldsPyculator(),
         #         EquivalentNumField(),
-        #         StatisticsByCategories(), ConcaveHull(),
+        #         StatisticsByCategories(),
         #         RasterLayerStatistics(), PointsDisplacement(),
         #         PointsFromPolygons(),
         #         PointsFromLines(), RandomPointsExtent(),
@@ -246,6 +246,7 @@ def getAlgs(self):
                 Boundary(),
                 BoundingBox(),
                 CheckValidity(),
+                ConcaveHull(),
                 CreateAttributeIndex(),
                 Delaunay(),
                 DeleteColumn(),