Move heatmap generation code to analysis lib

And clean it up a lot

Author: nyalldawson

python/analysis/analysis.sip

@@ -44,6 +44,7 @@
 %Include raster/qgsderivativefilter.sip
 %Include raster/qgsaspectfilter.sip
 %Include raster/qgshillshadefilter.sip
+%Include raster/qgskde.sip
 %Include raster/qgsninecellfilter.sip
 %Include raster/qgsrastercalcnode.sip
 %Include raster/qgsrastercalculator.sip

python/analysis/raster/qgskde.sip

@@ -0,0 +1,104 @@
+/**
+ * \class QgsKernelDensityEstimation
+ * \ingroup analysis
+ * Performs Kernel Density Estimation ("heatmap") calculations on a vector layer.
+ * @note added in QGIS 3.0
+ */
+class QgsKernelDensityEstimation
+{
+%TypeHeaderCode
+#include <qgskde.h>
+%End
+
+  public:
+
+    //! Kernel shape type
+    enum KernelShape
+    {
+      KernelQuartic, //!< Quartic kernel
+      KernelTriangular, //!< Triangular kernel
+      KernelUniform, //!< Uniform (flat) kernel
+      KernelTriweight, //!< Triweight kernel
+      KernelEpanechnikov, //!< Epanechnikov kernel
+    };
+
+    //! Output values type
+    enum OutputValues
+    {
+      OutputRaw, //!< Output the raw KDE values
+      OutputScaled, //!< Output mathematically correct scaled values
+    };
+
+    //! Result of operation
+    enum Result
+    {
+      Success, //!< Operation completed successfully
+      DriverError, //!< Could not open the driver for the specified format
+      InvalidParameters, //!< Input parameters were not valid
+      FileCreationError, //!< Error creating output file
+      RasterIoError, //!< Error writing to raster
+    };
+
+    //! KDE parameters
+    struct Parameters
+    {
+      //! Vector point layer
+      QgsVectorLayer* vectorLayer;
+
+      //! Fixed radius, in map units
+      double radius;
+
+      //! Field for radius, or empty if using a fixed radius
+      QString radiusField;
+
+      //! Field name for weighting field, or empty if not using weights
+      QString weightField;
+
+      //! Size of pixel in output file
+      double pixelSize;
+
+      //! Kernel shape
+      QgsKernelDensityEstimation::KernelShape shape;
+
+      //! Decay ratio (Triangular kernels only)
+      double decayRatio;
+
+      //! Type of output value
+      QgsKernelDensityEstimation::OutputValues outputValues;
+    };
+
+    /**
+     * Constructor for QgsKernelDensityEstimation. Requires a Parameters object specifying the options to use
+     * to generate the surface. The output path and file format are also required.
+     */
+    QgsKernelDensityEstimation( const Parameters& parameters, const QString& outputFile, const QString& outputFormat );
+
+    /**
+     * Runs the KDE calculation across the whole layer at once. Either call this method, or manually
+     * call run(), addFeature() and finalise() separately.
+     */
+    Result run();
+
+    /**
+     * Prepares the output file for writing and setups up the surface calculation. This must be called
+     * before adding features via addFeature().
+     * @see addFeature()
+     * @see finalise()
+     */
+    Result prepare();
+
+    /**
+     * Adds a single feature to the KDE surface. prepare() must be called before adding features.
+     * @see prepare()
+     * @see finalise()
+     */
+    Result addFeature( const QgsFeature& feature );
+
+    /**
+     * Finalises the output file. Must be called after adding all features via addFeature().
+     * @see prepare()
+     * @see addFeature()
+     */
+    Result finalise();
+
+};

src/analysis/CMakeLists.txt

@@ -27,6 +27,7 @@ SET(QGIS_ANALYSIS_SRCS
   raster/qgsruggednessfilter.cpp
   raster/qgsderivativefilter.cpp
   raster/qgshillshadefilter.cpp
+  raster/qgskde.cpp
   raster/qgsslopefilter.cpp
   raster/qgsaspectfilter.cpp
   raster/qgstotalcurvaturefilter.cpp
@@ -106,6 +107,7 @@ SET(QGIS_ANALYSIS_HDRS
   raster/qgsaspectfilter.h
   raster/qgsderivativefilter.h
   raster/qgshillshadefilter.h
+  raster/qgskde.h
   raster/qgsninecellfilter.h
   raster/qgsrastercalculator.h
   raster/qgsrelief.h