[FEATURE][processing] New algorithm to extend lines

Allows extending linestrings by a set distance at the start
and end of the line

python/plugins/processing/algs/help/qgis.yaml

@@ -158,6 +158,9 @@ qgis:exportaddgeometrycolumns: >
 
   Depending on the geometry type of the vector layer, the attributes added to the table will be different.
 
+qgis:extendlines: >
+  This algorithms extends line geometries by a specified amount at the start and end of the line. Lines are extended using the bearing of the first and last segment in the line.
+
 qgis:extractbyattribute: >
   This algorithms creates a new vector layer that only contains matching features from an input layer. The criteria for adding features to the resulting layer is defined based on the values of an attribute from the input layer.
 

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

@@ -0,0 +1,86 @@
+# -*- coding: utf-8 -*-
+
+"""
+***************************************************************************
+    ExtendLines.py
+    --------------------
+    Date                 : October 2016
+    Copyright            : (C) 2016 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__ = 'October 2016'
+__copyright__ = '(C) 2016, Nyall Dawson'
+
+# This will get replaced with a git SHA1 when you do a git archive323
+
+__revision__ = '$Format:%H$'
+
+
+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 ExtendLines(GeoAlgorithm):
+
+    INPUT_LAYER = 'INPUT_LAYER'
+    OUTPUT_LAYER = 'OUTPUT_LAYER'
+    START_DISTANCE = 'START_DISTANCE'
+    END_DISTANCE = 'END_DISTANCE'
+
+    def defineCharacteristics(self):
+        self.name, self.i18n_name = self.trAlgorithm('Extend lines')
+        self.group, self.i18n_group = self.trAlgorithm('Vector geometry tools')
+
+        self.addParameter(ParameterVector(self.INPUT_LAYER,
+                                          self.tr('Input layer'), [dataobjects.TYPE_VECTOR_LINE]))
+        self.addParameter(ParameterNumber(self.START_DISTANCE,
+                                          self.tr('Start distance'), default=0.0))
+        self.addParameter(ParameterNumber(self.END_DISTANCE,
+                                          self.tr('End distance'), default=0.0))
+
+        self.addOutput(OutputVector(self.OUTPUT_LAYER, self.tr('Extended lines')))
+
+    def processAlgorithm(self, progress):
+        layer = dataobjects.getObjectFromUri(
+            self.getParameterValue(self.INPUT_LAYER))
+
+        writer = self.getOutputFromName(
+            self.OUTPUT_LAYER).getVectorWriter(
+                layer.fields(),
+                layer.wkbType(),
+                layer.crs())
+
+        start_distance = self.getParameterValue(self.START_DISTANCE)
+        end_distance = self.getParameterValue(self.END_DISTANCE)
+
+        features = vector.features(layer)
+        total = 100.0 / len(features)
+
+        for current, input_feature in enumerate(features):
+            output_feature = input_feature
+            input_geometry = input_feature.geometry()
+            if input_geometry:
+                output_geometry = input_geometry.extendLine(start_distance, end_distance)
+                if not output_geometry:
+                    raise GeoAlgorithmExecutionException(
+                        self.tr('Error calculating extended line'))
+
+                output_feature.setGeometry(output_geometry)
+
+            writer.addFeature(output_feature)
+            progress.setPercentage(int(current * total))
+
+        del writer

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

@@ -171,6 +171,7 @@
 from .TinInterpolationAttribute import TinInterpolationAttribute
 from .ZonalStatisticsQgis import ZonalStatisticsQgis
 from .RemoveNullGeometry import RemoveNullGeometry
+from .ExtendLines import ExtendLines
 
 pluginPath = os.path.normpath(os.path.join(
     os.path.split(os.path.dirname(__file__))[0], os.pardir))
@@ -232,7 +233,7 @@ def __init__(self):
                         ReliefAuto(), ZonalStatisticsQgis(),
                         IdwInterpolationZValue(), IdwInterpolationAttribute(),
                         TinInterpolationZValue(), TinInterpolationAttribute(),
-                        RemoveNullGeometry(), ExtractByExpression()
+                        RemoveNullGeometry(), ExtractByExpression(), ExtendLines()
                         ]
 
         if hasMatplotlib:

python/plugins/processing/tests/testdata/expected/extend_lines.gfs

@@ -0,0 +1,15 @@
+<GMLFeatureClassList>
+  <GMLFeatureClass>
+    <Name>extend_lines</Name>
+    <ElementPath>extend_lines</ElementPath>
+    <GeometryType>2</GeometryType>
+    <SRSName>EPSG:4326</SRSName>
+    <DatasetSpecificInfo>
+      <FeatureCount>7</FeatureCount>
+      <ExtentXMin>-1.10000</ExtentXMin>
+      <ExtentXMax>11.14142</ExtentXMax>
+      <ExtentYMin>-3.07071</ExtentYMin>
+      <ExtentYMax>5.14142</ExtentYMax>
+    </DatasetSpecificInfo>
+  </GMLFeatureClass>
+</GMLFeatureClassList>

python/plugins/processing/tests/testdata/expected/extend_lines.gml

@@ -0,0 +1,48 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ogr:FeatureCollection
+     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+     xsi:schemaLocation=""
+     xmlns:ogr="http://ogr.maptools.org/"
+     xmlns:gml="http://www.opengis.net/gml">
+  <gml:boundedBy>
+    <gml:Box>
+      <gml:coord><gml:X>-1.1</gml:X><gml:Y>-3.070710678118655</gml:Y></gml:coord>
+      <gml:coord><gml:X>11.14142135623731</gml:X><gml:Y>5.141421356237309</gml:Y></gml:coord>
+    </gml:Box>
+  </gml:boundedBy>
+
+  <gml:featureMember>
+    <ogr:extend_lines fid="lines.0">
+      <ogr:geometryProperty><gml:LineString srsName="EPSG:4326"><gml:coordinates>5.9,2.0 9,2 9,3 11.141421356237309,5.141421356237309</gml:coordinates></gml:LineString></ogr:geometryProperty>
+    </ogr:extend_lines>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:extend_lines fid="lines.1">
+      <ogr:geometryProperty><gml:LineString srsName="EPSG:4326"><gml:coordinates>-1.1,-1.0 1.2,-1.0</gml:coordinates></gml:LineString></ogr:geometryProperty>
+    </ogr:extend_lines>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:extend_lines fid="lines.2">
+      <ogr:geometryProperty><gml:LineString srsName="EPSG:4326"><gml:coordinates>2.0,-0.1 2,2 3,2 3.0,3.2</gml:coordinates></gml:LineString></ogr:geometryProperty>
+    </ogr:extend_lines>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:extend_lines fid="lines.3">
+      <ogr:geometryProperty><gml:LineString srsName="EPSG:4326"><gml:coordinates>2.9,1.0 5.2,1.0</gml:coordinates></gml:LineString></ogr:geometryProperty>
+    </ogr:extend_lines>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:extend_lines fid="lines.4">
+      <ogr:geometryProperty><gml:LineString srsName="EPSG:4326"><gml:coordinates>6.9,-3.0 10.2,-3.0</gml:coordinates></gml:LineString></ogr:geometryProperty>
+    </ogr:extend_lines>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:extend_lines fid="lines.5">
+      <ogr:geometryProperty><gml:LineString srsName="EPSG:4326"><gml:coordinates>5.929289321881345,-3.070710678118655 10.141421356237309,1.141421356237309</gml:coordinates></gml:LineString></ogr:geometryProperty>
+    </ogr:extend_lines>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:extend_lines fid="lines.6">
+    </ogr:extend_lines>
+  </gml:featureMember>
+</ogr:FeatureCollection>

python/plugins/processing/tests/testdata/expected/extend_multilines.gfs

@@ -0,0 +1,15 @@
+<GMLFeatureClassList>
+  <GMLFeatureClass>
+    <Name>extend_multilines</Name>
+    <ElementPath>extend_multilines</ElementPath>
+    <GeometryType>5</GeometryType>
+    <SRSName>EPSG:4326</SRSName>
+    <DatasetSpecificInfo>
+      <FeatureCount>4</FeatureCount>
+      <ExtentXMin>-1.20000</ExtentXMin>
+      <ExtentXMax>5.98034</ExtentXMax>
+      <ExtentYMin>-1.00000</ExtentYMin>
+      <ExtentYMax>4.13130</ExtentYMax>
+    </DatasetSpecificInfo>
+  </GMLFeatureClass>
+</GMLFeatureClassList>

python/plugins/processing/tests/testdata/expected/extend_multilines.gml

@@ -0,0 +1,33 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ogr:FeatureCollection
+     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+     xsi:schemaLocation=""
+     xmlns:ogr="http://ogr.maptools.org/"
+     xmlns:gml="http://www.opengis.net/gml">
+  <gml:boundedBy>
+    <gml:Box>
+      <gml:coord><gml:X>-1.2</gml:X><gml:Y>-1</gml:Y></gml:coord>
+      <gml:coord><gml:X>5.980337387043503</gml:X><gml:Y>4.131303337656388</gml:Y></gml:coord>
+    </gml:Box>
+  </gml:boundedBy>
+
+  <gml:featureMember>
+    <ogr:extend_multilines fid="lines.1">
+      <ogr:geometryProperty><gml:MultiLineString srsName="EPSG:4326"><gml:lineStringMember><gml:LineString><gml:coordinates>-1.2,-1.0 1.4,-1.0</gml:coordinates></gml:LineString></gml:lineStringMember></gml:MultiLineString></ogr:geometryProperty>
+    </ogr:extend_multilines>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:extend_multilines fid="lines.2">
+      <ogr:geometryProperty><gml:MultiLineString srsName="EPSG:4326"><gml:lineStringMember><gml:LineString><gml:coordinates>2.8,1.0 5.4,1.0</gml:coordinates></gml:LineString></gml:lineStringMember><gml:lineStringMember><gml:LineString><gml:coordinates>5.027602565068266,2.614750056493599 4.993163391936403,0.600058428279599</gml:coordinates></gml:LineString></gml:lineStringMember></gml:MultiLineString></ogr:geometryProperty>
+    </ogr:extend_multilines>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:extend_multilines fid="lines.3">
+    </ogr:extend_multilines>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:extend_multilines fid="lines.4">
+      <ogr:geometryProperty><gml:MultiLineString srsName="EPSG:4326"><gml:lineStringMember><gml:LineString><gml:coordinates>2.0,-0.2 2,2 3,2 3.0,3.4</gml:coordinates></gml:LineString></gml:lineStringMember><gml:lineStringMember><gml:LineString><gml:coordinates>2.744420970065991,4.041450058619024 5.859334643361299,4.131303337656388</gml:coordinates></gml:LineString></gml:lineStringMember><gml:lineStringMember><gml:LineString><gml:coordinates>2.800042438915868,3.004119922970864 5.980337387043503,2.938593167493973</gml:coordinates></gml:LineString></gml:lineStringMember></gml:MultiLineString></ogr:geometryProperty>
+    </ogr:extend_multilines>
+  </gml:featureMember>
+</ogr:FeatureCollection>

python/plugins/processing/tests/testdata/qgis_algorithm_tests.yaml

@@ -1225,3 +1225,30 @@ tests:
       OUTPUT:
         name: expected/extract_expression.gml
         type: vector
+
+  - algorithm: qgis:extendlines
+    name: Extend lines
+    params:
+      END_DISTANCE: 0.2
+      INPUT_LAYER:
+        name: lines.gml
+        type: vector
+      START_DISTANCE: 0.1
+    results:
+      OUTPUT_LAYER:
+        name: expected/extend_lines.gml
+        type: vector
+
+
+  - algorithm: qgis:extendlines
+    name: Extend multilines
+    params:
+      END_DISTANCE: 0.4
+      INPUT_LAYER:
+        name: multilines.gml
+        type: vector
+      START_DISTANCE: 0.2
+    results:
+      OUTPUT_LAYER:
+        name: expected/extend_multilines.gml
+        type: vector