Merge pull request #42648 from roya0045/fix_mainangle

[Bugfix] geometry engine::main_angle : promote longer box in case of tie
qgis · Oct 11, 2021 · 1666afe · 1666afe
2 parents 7a0fb2a + 6a717fc
commit 1666afe
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Showing 4 changed files with 11 additions and 2 deletions.
diff --git a/resources/function_help/json/main_angle b/resources/function_help/json/main_angle
@@ -2,7 +2,7 @@
   "name": "main_angle",
   "type": "function",
   "groups": ["GeometryGroup"],
-  "description":"Returns the main angle of a geometry (clockwise, in degrees from North), which represents the angle of the oriented minimal bounding rectangle which completely covers the geometry.",
+  "description":"Returns the angle of the long axis (clockwise, in degrees from North) of the oriented minimal bounding rectangle, which completely covers the geometry.",
   "arguments": [ {"arg":"geometry","description":"a geometry"} ],
   "examples": [ { "expression":"main_angle(geom_from_wkt('Polygon ((321577 129614, 321581 129618, 321585 129615, 321581 129610, 321577 129614))'))", "returns":"38.66"}]
 }

diff --git a/src/core/geometry/qgsinternalgeometryengine.cpp b/src/core/geometry/qgsinternalgeometryengine.cpp
@@ -1629,6 +1629,13 @@ QgsGeometry QgsInternalGeometryEngine::orientedMinimumBoundingBox( double &area,
     pt1 = hull->vertexAt( vertexId );
   }
 
+  if ( width > height )
+  {
+    width = minRect.height();
+    height = minRect.width();
+    angle = angle + 90.0;
+  }
+
   QgsGeometry minBounds = QgsGeometry::fromRect( minRect );
   minBounds.rotate( angle, QgsPointXY( pt0.x(), pt0.y() ) );
 

diff --git a/src/core/geometry/qgsinternalgeometryengine.h b/src/core/geometry/qgsinternalgeometryengine.h
@@ -213,7 +213,8 @@ class QgsInternalGeometryEngine
 
     /**
      * Returns the oriented minimum bounding box for the geometry, which is the smallest (by area)
-     * rotated rectangle which fully encompasses the geometry. The area, angle (clockwise in degrees from North),
+     * rotated rectangle which fully encompasses the geometry.
+     * The area, angle of the long axis (clockwise in degrees from North),
      * width and height of the rotated bounding box will also be returned.
      *
      * If an error was encountered while creating the result, more information can be retrieved

diff --git a/tests/src/core/testqgsexpression.cpp b/tests/src/core/testqgsexpression.cpp
@@ -1358,6 +1358,7 @@ class TestQgsExpression: public QObject
       QTest::newRow( "m_min line M NaN" ) << "m_min(make_line(geom_from_wkt('PointZM (0 0 0 nan)'),geom_from_wkt('PointZM (1 1 1 2)')))" << false << QVariant( );
       QTest::newRow( "m_min line" ) << "m_min(make_line(make_point_m(0,0,1),make_point_m(-1,-1,2),make_point_m(-2,-2,0)))" << false << QVariant( 0.0 );
       QTest::newRow( "main angle polygon" ) << "round(main_angle( geom_from_wkt('POLYGON((0 0,2 9,9 2,0 0))')))" << false << QVariant( 77 );
+      QTest::newRow( "main angle polygon edge case" ) << "round(main_angle( geom_from_wkt('POLYGON((353542.63843526 378974.92373469, 353544.95808017 378975.73690545, 353545.27173175 378974.84218528, 353542.95208684 378974.02901451, 353542.63843526 378974.92373469))')))" << false << QVariant( 71 );
       QTest::newRow( "main angle multi polygon" ) << "round(main_angle( geom_from_wkt('MULTIPOLYGON(((0 0,3 10,1 10,1 6,0 0)))')))" << false << QVariant( 17 );
       QTest::newRow( "main angle point" ) << "main_angle( geom_from_wkt('POINT (1.5 0.5)') )" << true << QVariant();
       QTest::newRow( "main angle line" ) << "round(main_angle( geom_from_wkt('LINESTRING (-1 2, 9 12)') ))" << false << QVariant( 45 );