Better constructor, dox

qgis · Jun 8, 2018 · 6bf7c0e · 6bf7c0e
1 parent e97f0d3
commit 6bf7c0e
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Showing 3 changed files with 44 additions and 16 deletions.
diff --git a/python/analysis/auto_generated/vector/qgszonalstatistics.sip.in b/python/analysis/auto_generated/vector/qgszonalstatistics.sip.in
@@ -15,7 +15,7 @@
 class QgsZonalStatistics
 {
 %Docstring
-A class that calculates raster statistics (count, sum, mean) for a polygon or multipolygon layer and appends the results as attributes*
+A class that calculates raster statistics (count, sum, mean) for a polygon or multipolygon layer and appends the results as attributes.
 %End
 
 %TypeHeaderCode
@@ -69,6 +69,24 @@ The raster layer must exist for the lifetime of the zonal statistics calculation
 %Docstring
 Constructor for QgsZonalStatistics, using a QgsRasterInterface.
 
+The ``polygonLayer`` gives the vector layer containing the (multi)polygon features corresponding to the
+different zones. This layer will be modified, adding extra attributes for each of the zonal statistics
+calculated.
+
+Pixel values for each zone are taken from the raster ``rasterInterface``. The constructor must also
+be given various properties relating to the input raster, such as the raster CRS (``rasterCrs``),
+and the size (X and Y) in map units for each raster pixel. The source raster band is specified
+via ``rasterBand``, where a value of 1 corresponds to the first band.
+
+If the CRS of the ``polygonLayer`` and ``rasterCrs`` differ, the calculation will automatically
+reproject the zones to ensure valid results are calculated.
+
+The ``attributePrefix`` argument specifies an optional prefix to use when creating the
+new fields for each calculated statistic.
+
+Finally, the calculated statistics can be set via the ``stats`` argument. A new field will be
+added to ``polygonLayer`` for each statistic calculated.
+
 .. warning::
 
    The raster interface must exist for the lifetime of the zonal statistics calculation. For thread
@@ -77,12 +95,11 @@ Constructor for QgsZonalStatistics, using a QgsRasterInterface.
 .. versionadded:: 3.2
 %End
 
-
     int calculateStatistics( QgsFeedback *feedback );
 %Docstring
 Starts the calculation
 
-:return: 0 in case of success*
+:return: 0 in case of success
 %End
 
       public:

diff --git a/src/analysis/vector/qgszonalstatistics.cpp b/src/analysis/vector/qgszonalstatistics.cpp
@@ -46,21 +46,13 @@ QgsZonalStatistics::QgsZonalStatistics( QgsVectorLayer *polygonLayer, QgsRasterI
                                         const QgsCoordinateReferenceSystem &rasterCrs, double rasterUnitsPerPixelX, double rasterUnitsPerPixelY, const QString &attributePrefix, int rasterBand, QgsZonalStatistics::Statistics stats )
   : mRasterInterface( rasterInterface )
   , mRasterCrs( rasterCrs )
-  , mCellSizeX( rasterUnitsPerPixelX )
-  , mCellSizeY( rasterUnitsPerPixelY )
+  , mCellSizeX( std::fabs( rasterUnitsPerPixelX ) )
+  , mCellSizeY( std::fabs( rasterUnitsPerPixelY ) )
   , mRasterBand( rasterBand )
   , mPolygonLayer( polygonLayer )
   , mAttributePrefix( attributePrefix )
   , mStatistics( stats )
 {
-  if ( mCellSizeX < 0 )
-  {
-    mCellSizeX = -mCellSizeX;
-  }
-  if ( mCellSizeY < 0 )
-  {
-    mCellSizeY = -mCellSizeY;
-  }
 }
 
 int QgsZonalStatistics::calculateStatistics( QgsFeedback *feedback )

diff --git a/src/analysis/vector/qgszonalstatistics.h b/src/analysis/vector/qgszonalstatistics.h
@@ -38,7 +38,8 @@ class QgsField;
 
 /**
  * \ingroup analysis
- *  A class that calculates raster statistics (count, sum, mean) for a polygon or multipolygon layer and appends the results as attributes*/
+ * A class that calculates raster statistics (count, sum, mean) for a polygon or multipolygon layer and appends the results as attributes.
+*/
 class ANALYSIS_EXPORT QgsZonalStatistics
 {
   public:
@@ -79,6 +80,24 @@ class ANALYSIS_EXPORT QgsZonalStatistics
     /**
      * Constructor for QgsZonalStatistics, using a QgsRasterInterface.
      *
+     * The \a polygonLayer gives the vector layer containing the (multi)polygon features corresponding to the
+     * different zones. This layer will be modified, adding extra attributes for each of the zonal statistics
+     * calculated.
+     *
+     * Pixel values for each zone are taken from the raster \a rasterInterface. The constructor must also
+     * be given various properties relating to the input raster, such as the raster CRS (\a rasterCrs),
+     * and the size (X and Y) in map units for each raster pixel. The source raster band is specified
+     * via \a rasterBand, where a value of 1 corresponds to the first band.
+     *
+     * If the CRS of the \a polygonLayer and \a rasterCrs differ, the calculation will automatically
+     * reproject the zones to ensure valid results are calculated.
+     *
+     * The \a attributePrefix argument specifies an optional prefix to use when creating the
+     * new fields for each calculated statistic.
+     *
+     * Finally, the calculated statistics can be set via the \a stats argument. A new field will be
+     * added to \a polygonLayer for each statistic calculated.
+     *
      * \warning The raster interface must exist for the lifetime of the zonal statistics calculation. For thread
      * safe use, always use a cloned raster interface.
      *
@@ -93,10 +112,10 @@ class ANALYSIS_EXPORT QgsZonalStatistics
                         int rasterBand = 1,
                         QgsZonalStatistics::Statistics stats = QgsZonalStatistics::Statistics( QgsZonalStatistics::Count | QgsZonalStatistics::Sum | QgsZonalStatistics::Mean ) );
 
-
     /**
      * Starts the calculation
-      \returns 0 in case of success*/
+     * \returns 0 in case of success
+    */
     int calculateStatistics( QgsFeedback *feedback );
 
   private: