Merge pull request #3391 from nyalldawson/single_sided

Single sided buffers
qgis · Aug 16, 2016 · f5b1715 · f5b1715
2 parents 40b70a3 + d193574
commit f5b1715
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Showing 28 changed files with 666 additions and 184 deletions.
diff --git a/cmake/FindGEOS.cmake b/cmake/FindGEOS.cmake
@@ -87,9 +87,9 @@ ELSE(WIN32)
         STRING(REGEX REPLACE "([0-9]+)\\.([0-9]+)\\.([0-9]+)" "\\1" GEOS_VERSION_MAJOR "${GEOS_VERSION}")
         STRING(REGEX REPLACE "([0-9]+)\\.([0-9]+)\\.([0-9]+)" "\\2" GEOS_VERSION_MINOR "${GEOS_VERSION}")
 
-        IF (GEOS_VERSION_MAJOR LESS 3 OR (GEOS_VERSION_MAJOR EQUAL 3 AND GEOS_VERSION_MINOR LESS 1) )
-          MESSAGE (FATAL_ERROR "GEOS version is too old (${GEOS_VERSION}). Use 3.1.0 or higher.")
-        ENDIF (GEOS_VERSION_MAJOR LESS 3 OR (GEOS_VERSION_MAJOR EQUAL 3 AND GEOS_VERSION_MINOR LESS 1) )
+        IF (GEOS_VERSION_MAJOR LESS 3 OR (GEOS_VERSION_MAJOR EQUAL 3 AND GEOS_VERSION_MINOR LESS 3) )
+          MESSAGE (FATAL_ERROR "GEOS version is too old (${GEOS_VERSION}). Use 3.3.0 or higher.")
+        ENDIF (GEOS_VERSION_MAJOR LESS 3 OR (GEOS_VERSION_MAJOR EQUAL 3 AND GEOS_VERSION_MINOR LESS 3) )
 
         # set INCLUDE_DIR to prefix+include
         EXEC_PROGRAM(${GEOS_CONFIG}

diff --git a/python/core/geometry/qgsgeometry.sip b/python/core/geometry/qgsgeometry.sip
@@ -447,27 +447,67 @@ class QgsGeometry
      *  @note added in 1.5 */
     bool crosses( const QgsGeometry& geometry ) const;
 
+    //! Side of line to buffer
+    enum BufferSide
+    {
+      SideLeft, //!< Buffer to left of line
+      SideRight, //!< Buffer to right of line
+    };
+
+    //! End cap styles for buffers
+    enum EndCapStyle
+    {
+      CapRound, //!< Round cap
+      CapFlat, //!< Flat cap (in line with start/end of line)
+      CapSquare, //!< Square cap (extends past start/end of line by buffer distance)
+    };
+
+    //! Join styles for buffers
+    enum JoinStyle
+    {
+      JoinStyleRound, //!< Use rounded joins
+      JoinStyleMitre, //!< Use mitred joins
+      JoinStyleBevel, //!< Use beveled joins
+    };
+
     /** Returns a buffer region around this geometry having the given width and with a specified number
         of segments used to approximate curves */
     QgsGeometry buffer( double distance, int segments ) const;
 
     /** Returns a buffer region around the geometry, with additional style options.
      * @param distance    buffer distance
-     * @param segments    For round joins, number of segments to approximate quarter-circle
-     * @param endCapStyle Round (1) / Flat (2) / Square (3) end cap style
-     * @param joinStyle   Round (1) / Mitre (2) / Bevel (3) join style
-     * @param mitreLimit  Limit on the mitre ratio used for very sharp corners
+     * @param segments    for round joins, number of segments to approximate quarter-circle
+     * @param endCapStyle end cap style
+     * @param joinStyle   join style for corners in geometry
+     * @param mitreLimit  limit on the mitre ratio used for very sharp corners (JoinStyleMitre only)
      * @note added in 2.4
-     * @note needs GEOS >= 3.3 - otherwise always returns 0
      */
-    QgsGeometry buffer( double distance, int segments, int endCapStyle, int joinStyle, double mitreLimit ) const;
+    QgsGeometry buffer( double distance, int segments, EndCapStyle endCapStyle, JoinStyle joinStyle, double mitreLimit ) const;
 
     /** Returns an offset line at a given distance and side from an input line.
-     * See buffer() method for details on parameters.
+     * @param distance    buffer distance
+     * @param segments    for round joins, number of segments to approximate quarter-circle
+     * @param joinStyle   join style for corners in geometry
+     * @param mitreLimit  limit on the mitre ratio used for very sharp corners (JoinStyleMitre only)
      * @note added in 2.4
-     * @note needs GEOS >= 3.3 - otherwise always returns 0
      */
-    QgsGeometry offsetCurve( double distance, int segments, int joinStyle, double mitreLimit ) const;
+    QgsGeometry offsetCurve( double distance, int segments, JoinStyle joinStyle, double mitreLimit ) const;
+
+    /**
+     * Returns a single sided buffer for a (multi)line geometry. The buffer is only
+     * applied to one side of the line.
+     * @param distance buffer distance
+     * @param segments for round joins, number of segments to approximate quarter-circle
+     * @param side side of geometry to buffer
+     * @param joinStyle join style for corners
+     * @param mitreLimit limit on the mitre ratio used for very sharp corners
+     * @return buffered geometry, or an empty geometry if buffer could not be
+     * calculated
+     * @note added in QGIS 3.0
+     */
+    QgsGeometry singleSidedBuffer( double distance, int segments, BufferSide side,
+                                   JoinStyle joinStyle = JoinStyleRound,
+                                   double mitreLimit = 2.0 ) const;
 
     /** Returns a simplified version of this geometry using a specified tolerance value */
     QgsGeometry simplify( double tolerance )  const;

diff --git a/python/plugins/processing/algs/help/qgis.yaml b/python/plugins/processing/algs/help/qgis.yaml
@@ -425,6 +425,15 @@ qgis:simplifygeometries: >
 qgis:singlepartstomultipart:
 
 
+qgis:singlesidedbuffer: >
+  This algorithm buffers lines by a specified distance on one side of the line only.
+
+  The segments parameter controls the number of line segments to use to approximate a quarter circle when creating rounded buffers.
+
+  The join style parameter specifies whether round, mitre or beveled joins should be used when buffering corners in a line.
+
+  The mitre limit parameter is only applicable for mitre join styles, and controls the maximum distance from the buffer to use when creating a mitred join.
+
 qgis:snappointstogrid: >
   This algorithm modifies the position of points in a vector layer, so they fall in the coordinates of a grid.
 

diff --git a/python/plugins/processing/algs/qgis/QGISAlgorithmProvider.py b/python/plugins/processing/algs/qgis/QGISAlgorithmProvider.py
@@ -153,6 +153,7 @@
 from .OffsetLine import OffsetLine
 from .PolygonCentroids import PolygonCentroids
 from .Translate import Translate
+from .SingleSidedBuffer import SingleSidedBuffer
 
 pluginPath = os.path.normpath(os.path.join(
     os.path.split(os.path.dirname(__file__))[0], os.pardir))
@@ -207,7 +208,7 @@ def __init__(self):
                         RectanglesOvalsDiamondsFixed(), MergeLines(),
                         BoundingBox(), Boundary(), PointOnSurface(),
                         OffsetLine(), PolygonCentroids(),
-                        Translate()
+                        Translate(), SingleSidedBuffer()
                         ]
 
         if hasMatplotlib:

diff --git a/python/plugins/processing/algs/qgis/SingleSidedBuffer.py b/python/plugins/processing/algs/qgis/SingleSidedBuffer.py
@@ -0,0 +1,118 @@
+# -*- coding: utf-8 -*-
+
+"""
+***************************************************************************
+    SingleSidedBuffer.py
+    --------------------
+    Date                 : August 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__ = 'August 2016'
+__copyright__ = '(C) 2016, Nyall Dawson'
+
+# This will get replaced with a git SHA1 when you do a git archive323
+
+__revision__ = '$Format:%H$'
+
+import os
+
+from qgis.core import QgsGeometry, QgsWkbTypes
+
+from processing.core.GeoAlgorithm import GeoAlgorithm
+from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
+from processing.core.parameters import ParameterVector, ParameterSelection, ParameterNumber
+from processing.core.outputs import OutputVector
+from processing.tools import dataobjects, vector
+
+pluginPath = os.path.split(os.path.split(os.path.dirname(__file__))[0])[0]
+
+
+class SingleSidedBuffer(GeoAlgorithm):
+
+    INPUT_LAYER = 'INPUT_LAYER'
+    OUTPUT_LAYER = 'OUTPUT_LAYER'
+    DISTANCE = 'DISTANCE'
+    SIDE = 'SIDE'
+    SEGMENTS = 'SEGMENTS'
+    JOIN_STYLE = 'JOIN_STYLE'
+    MITRE_LIMIT = 'MITRE_LIMIT'
+
+    def defineCharacteristics(self):
+        self.name, self.i18n_name = self.trAlgorithm('Single sided buffer')
+        self.group, self.i18n_group = self.trAlgorithm('Vector geometry tools')
+
+        self.addParameter(ParameterVector(self.INPUT_LAYER,
+                                          self.tr('Input layer'), [ParameterVector.VECTOR_TYPE_LINE]))
+        self.addParameter(ParameterNumber(self.DISTANCE,
+                                          self.tr('Distance'), default=10.0))
+        self.sides = [self.tr('Left'),
+                      'Right']
+        self.addParameter(ParameterSelection(
+            self.SIDE,
+            self.tr('Side'),
+            self.sides))
+
+        self.addParameter(ParameterNumber(self.SEGMENTS,
+                                          self.tr('Segments'), 1, default=8))
+
+        self.join_styles = [self.tr('Round'),
+                            'Mitre',
+                            'Bevel']
+        self.addParameter(ParameterSelection(
+            self.JOIN_STYLE,
+            self.tr('Join style'),
+            self.join_styles))
+        self.addParameter(ParameterNumber(self.MITRE_LIMIT,
+                                          self.tr('Mitre limit'), 1, default=2))
+
+        self.addOutput(OutputVector(self.OUTPUT_LAYER, self.tr('Single sided buffers')))
+
+    def processAlgorithm(self, progress):
+        layer = dataobjects.getObjectFromUri(
+            self.getParameterValue(self.INPUT_LAYER))
+
+        writer = self.getOutputFromName(
+            self.OUTPUT_LAYER).getVectorWriter(
+                layer.fields().toList(),
+                QgsWkbTypes.Polygon,
+                layer.crs())
+
+        distance = self.getParameterValue(self.DISTANCE)
+        segments = int(self.getParameterValue(self.SEGMENTS))
+        join_style = self.getParameterValue(self.JOIN_STYLE) + 1
+        if self.getParameterValue(self.SIDE) == 0:
+            side = QgsGeometry.SideLeft
+        else:
+            side = QgsGeometry.SideRight
+        miter_limit = self.getParameterValue(self.MITRE_LIMIT)
+
+        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.singleSidedBuffer(distance, segments,
+                                                                   side, join_style, miter_limit)
+                if not output_geometry:
+                    raise GeoAlgorithmExecutionException(
+                        self.tr('Error calculating single sided buffer'))
+
+                output_feature.setGeometry(output_geometry)
+
+            writer.addFeature(output_feature)
+            progress.setPercentage(int(current * total))
+
+        del writer
diff --git a/python/plugins/processing/tests/testdata/expected/single_sided_buffer_line.gfs b/python/plugins/processing/tests/testdata/expected/single_sided_buffer_line.gfs
@@ -0,0 +1,15 @@
+<GMLFeatureClassList>
+  <GMLFeatureClass>
+    <Name>single_sided_buffer_line</Name>
+    <ElementPath>single_sided_buffer_line</ElementPath>
+    <GeometryType>3</GeometryType>
+    <SRSName>EPSG:4326</SRSName>
+    <DatasetSpecificInfo>
+      <FeatureCount>7</FeatureCount>
+      <ExtentXMin>-1.00000</ExtentXMin>
+      <ExtentXMax>11.00000</ExtentXMax>
+      <ExtentYMin>-3.00000</ExtentYMin>
+      <ExtentYMax>5.70711</ExtentYMax>
+    </DatasetSpecificInfo>
+  </GMLFeatureClass>
+</GMLFeatureClassList>
diff --git a/python/plugins/processing/tests/testdata/expected/single_sided_buffer_line.gml b/python/plugins/processing/tests/testdata/expected/single_sided_buffer_line.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</gml:X><gml:Y>-3</gml:Y></gml:coord>
+      <gml:coord><gml:X>11</gml:X><gml:Y>5.707106781186548</gml:Y></gml:coord>
+    </gml:Box>
+  </gml:boundedBy>
+
+  <gml:featureMember>
+    <ogr:single_sided_buffer_line fid="lines.0">
+      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>11,5 9,3 9,2 6,2 6,3 8,3 8.01921471959677,3.195090322016128 8.076120467488714,3.38268343236509 8.168530387697455,3.555570233019602 8.292893218813452,3.707106781186547 10.292893218813452,5.707106781186548 11,5</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
+    </ogr:single_sided_buffer_line>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:single_sided_buffer_line fid="lines.1">
+      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>1,-1 -1,-1 -1,0 1,0 1,-1</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
+    </ogr:single_sided_buffer_line>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:single_sided_buffer_line fid="lines.2">
+      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>3,3 3,2 2,2 2,0 1,0 1,2 1.01921471959677,2.195090322016128 1.076120467488713,2.38268343236509 1.168530387697455,2.555570233019602 1.292893218813453,2.707106781186547 1.444429766980398,2.831469612302545 1.61731656763491,2.923879532511287 1.804909677983872,2.98078528040323 2,3 3,3</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
+    </ogr:single_sided_buffer_line>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:single_sided_buffer_line fid="lines.3">
+      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>5,1 3,1 3,2 5,2 5,1</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
+    </ogr:single_sided_buffer_line>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:single_sided_buffer_line fid="lines.4">
+      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>10,-3 7,-3 7,-2 10,-2 10,-3</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
+    </ogr:single_sided_buffer_line>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:single_sided_buffer_line fid="lines.5">
+      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>10,1 6,-3 5.292893218813452,-2.292893218813453 9.292893218813452,1.707106781186547 10,1</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
+    </ogr:single_sided_buffer_line>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:single_sided_buffer_line fid="lines.6">
+    </ogr:single_sided_buffer_line>
+  </gml:featureMember>
+</ogr:FeatureCollection>
diff --git a/python/plugins/processing/tests/testdata/expected/single_sided_buffer_line_mitre.gfs b/python/plugins/processing/tests/testdata/expected/single_sided_buffer_line_mitre.gfs
@@ -0,0 +1,15 @@
+<GMLFeatureClassList>
+  <GMLFeatureClass>
+    <Name>single_sided_buffer_line_mitre</Name>
+    <ElementPath>single_sided_buffer_line_mitre</ElementPath>
+    <GeometryType>3</GeometryType>
+    <SRSName>EPSG:4326</SRSName>
+    <DatasetSpecificInfo>
+      <FeatureCount>7</FeatureCount>
+      <ExtentXMin>-1.00000</ExtentXMin>
+      <ExtentXMax>11.70711</ExtentXMax>
+      <ExtentYMin>-4.00000</ExtentYMin>
+      <ExtentYMax>5.00000</ExtentYMax>
+    </DatasetSpecificInfo>
+  </GMLFeatureClass>
+</GMLFeatureClassList>
diff --git a/python/plugins/processing/tests/testdata/expected/single_sided_buffer_line_mitre.gml b/python/plugins/processing/tests/testdata/expected/single_sided_buffer_line_mitre.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</gml:X><gml:Y>-4</gml:Y></gml:coord>
+      <gml:coord><gml:X>11.70710678118655</gml:X><gml:Y>5</gml:Y></gml:coord>
+    </gml:Box>
+  </gml:boundedBy>
+
+  <gml:featureMember>
+    <ogr:single_sided_buffer_line_mitre fid="lines.0">
+      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>6,2 9,2 9,3 11,5 11.707106781186548,4.292893218813452 10.0,2.585786437626905 10,1 6,1 6,2</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
+    </ogr:single_sided_buffer_line_mitre>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:single_sided_buffer_line_mitre fid="lines.1">
+      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>-1,-1 1,-1 1,-2 -1,-2 -1,-1</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
+    </ogr:single_sided_buffer_line_mitre>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:single_sided_buffer_line_mitre fid="lines.2">
+      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>2,0 2,2 3,2 3,3 4,3 4,1 3,1 3,0 2,0</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
+    </ogr:single_sided_buffer_line_mitre>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:single_sided_buffer_line_mitre fid="lines.3">
+      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>3,1 5,1 5,0 3,0 3,1</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
+    </ogr:single_sided_buffer_line_mitre>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:single_sided_buffer_line_mitre fid="lines.4">
+      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>7,-3 10,-3 10,-4 7,-4 7,-3</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
+    </ogr:single_sided_buffer_line_mitre>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:single_sided_buffer_line_mitre fid="lines.5">
+      <ogr:geometryProperty><gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>6,-3 10,1 10.707106781186548,0.292893218813453 6.707106781186548,-3.707106781186547 6,-3</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></ogr:geometryProperty>
+    </ogr:single_sided_buffer_line_mitre>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:single_sided_buffer_line_mitre fid="lines.6">
+    </ogr:single_sided_buffer_line_mitre>
+  </gml:featureMember>
+</ogr:FeatureCollection>
diff --git a/python/plugins/processing/tests/testdata/expected/single_sided_buffer_multiline_bevel.gfs b/python/plugins/processing/tests/testdata/expected/single_sided_buffer_multiline_bevel.gfs
@@ -0,0 +1,14 @@
+<GMLFeatureClassList>
+  <GMLFeatureClass>
+    <Name>single_sided_buffer_multiline_bevel</Name>
+    <ElementPath>single_sided_buffer_multiline_bevel</ElementPath>
+    <SRSName>EPSG:4326</SRSName>
+    <DatasetSpecificInfo>
+      <FeatureCount>4</FeatureCount>
+      <ExtentXMin>-1.00000</ExtentXMin>
+      <ExtentXMax>6.02404</ExtentXMax>
+      <ExtentYMin>-1.00000</ExtentYMin>
+      <ExtentYMax>5.11935</ExtentYMax>
+    </DatasetSpecificInfo>
+  </GMLFeatureClass>
+</GMLFeatureClassList>