QGIS API Documentation 3.37.0-Master (e33697b083e)
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Classes | Public Member Functions | Static Public Member Functions | List of all members
QgsZonalStatistics Class Reference

A class that calculates raster statistics (count, sum, mean) for a polygon or multipolygon layer and appends the results as attributes. More...

#include <qgszonalstatistics.h>

Public Member Functions

 QgsZonalStatistics (QgsVectorLayer *polygonLayer, QgsRasterInterface *rasterInterface, const QgsCoordinateReferenceSystem &rasterCrs, double rasterUnitsPerPixelX, double rasterUnitsPerPixelY, const QString &attributePrefix=QString(), int rasterBand=1, Qgis::ZonalStatistics stats=Qgis::ZonalStatistic::Default)
 Constructor for QgsZonalStatistics, using a QgsRasterInterface.
 
 QgsZonalStatistics (QgsVectorLayer *polygonLayer, QgsRasterLayer *rasterLayer, const QString &attributePrefix=QString(), int rasterBand=1, Qgis::ZonalStatistics stats=Qgis::ZonalStatistic::Default)
 Convenience constructor for QgsZonalStatistics, using an input raster layer.
 
Qgis::ZonalStatisticResult calculateStatistics (QgsFeedback *feedback)
 Runs the calculation.
 

Static Public Member Functions

static QMap< Qgis::ZonalStatistic, QVariant > calculateStatistics (QgsRasterInterface *rasterInterface, const QgsGeometry &geometry, double cellSizeX, double cellSizeY, int rasterBand, Qgis::ZonalStatistics statistics)
 Calculates the specified statistics for the pixels of rasterBand in rasterInterface (a raster layer dataProvider() ) within polygon geometry.
 
static QString displayName (Qgis::ZonalStatistic statistic)
 Returns the friendly display name for a statistic.
 
static QString shortName (Qgis::ZonalStatistic statistic)
 Returns a short, friendly display name for a statistic, suitable for use in a field name.
 

Detailed Description

A class that calculates raster statistics (count, sum, mean) for a polygon or multipolygon layer and appends the results as attributes.

Definition at line 46 of file qgszonalstatistics.h.

Constructor & Destructor Documentation

◆ QgsZonalStatistics() [1/2]

QgsZonalStatistics::QgsZonalStatistics ( QgsVectorLayer polygonLayer,
QgsRasterLayer rasterLayer,
const QString &  attributePrefix = QString(),
int  rasterBand = 1,
Qgis::ZonalStatistics  stats = Qgis::ZonalStatistic::Default 
)

Convenience constructor for QgsZonalStatistics, using an input raster layer.

The raster layer must exist for the lifetime of the zonal statistics calculation.

Warning
Constructing QgsZonalStatistics using this method is not thread safe, and the constructor which accepts a QgsRasterInterface should be used instead.

Definition at line 31 of file qgszonalstatistics.cpp.

◆ QgsZonalStatistics() [2/2]

QgsZonalStatistics::QgsZonalStatistics ( QgsVectorLayer polygonLayer,
QgsRasterInterface rasterInterface,
const QgsCoordinateReferenceSystem rasterCrs,
double  rasterUnitsPerPixelX,
double  rasterUnitsPerPixelY,
const QString &  attributePrefix = QString(),
int  rasterBand = 1,
Qgis::ZonalStatistics  stats = Qgis::ZonalStatistic::Default 
)

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 safe use, always use a cloned raster interface.
Since
QGIS 3.2

Definition at line 43 of file qgszonalstatistics.cpp.

Member Function Documentation

◆ calculateStatistics() [1/2]

Qgis::ZonalStatisticResult QgsZonalStatistics::calculateStatistics ( QgsFeedback feedback)

Runs the calculation.

Definition at line 56 of file qgszonalstatistics.cpp.

◆ calculateStatistics() [2/2]

QMap< Qgis::ZonalStatistic, QVariant > QgsZonalStatistics::calculateStatistics ( QgsRasterInterface rasterInterface,
const QgsGeometry geometry,
double  cellSizeX,
double  cellSizeY,
int  rasterBand,
Qgis::ZonalStatistics  statistics 
)
static

Calculates the specified statistics for the pixels of rasterBand in rasterInterface (a raster layer dataProvider() ) within polygon geometry.

Returns a map of statistic to result value.

Since
QGIS 3.16

Definition at line 303 of file qgszonalstatistics.cpp.

◆ displayName()

QString QgsZonalStatistics::displayName ( Qgis::ZonalStatistic  statistic)
static

Returns the friendly display name for a statistic.

See also
shortName()
Since
QGIS 3.12

Definition at line 220 of file qgszonalstatistics.cpp.

◆ shortName()

QString QgsZonalStatistics::shortName ( Qgis::ZonalStatistic  statistic)
static

Returns a short, friendly display name for a statistic, suitable for use in a field name.

See also
displayName()
Since
QGIS 3.12

Definition at line 255 of file qgszonalstatistics.cpp.


The documentation for this class was generated from the following files: