Use Choropleth Map to Visualize Spatial Join Query (GeoSpark + Babylon)

GeoSparkAndBabylon.java

/*---------------------------- Step 0: Create GeoSpark Spatial RDDs ----------------------------*/
PointRDD spatialRDD = new PointRDD(sparkContext, PointInputLocation, PointOffset, FileDataSplitter.CSV, false, PointNumPartitions, StorageLevel.MEMORY_ONLY());
PolygonRDD queryRDD = new PolygonRDD(sparkContext, PolygonInputLocation,  FileDataSplitter.CSV, false, PolygonNumPartitions, StorageLevel.MEMORY_ONLY());
/*---------------------------- Step 1: Issue GeoSpark Spatial Join Query with Index ----------------------------*/
spatialRDD.spatialPartitioning(GridType.RTREE);
queryRDD.spatialPartitioning(spatialRDD.grids);
spatialRDD.buildIndex(IndexType.RTREE,true);
JavaPairRDD<Polygon,Long> joinResult = JoinQuery.SpatialJoinQueryCountByKey(spatialRDD,queryRDD,true, true);
/*---------------------------- Step 2: Create Babylon Choropleth Map using Twitter dataset ----------------------------*/
ChoroplethMap visualizationOperator = new ChoroplethMap(1000,600,USMainLandBoundary,false);
visualizationOperator.CustomizeColor(255, 255, 255, 255, Color.RED, true);
visualizationOperator.Visualize(sparkContext, joinResult);
/*---------------------------- Step 3: Create Babylon Scatteer Plot using USA county boundaries ----------------------------*/
ScatterPlot frontImage = new ScatterPlot(1000,600,USMainLandBoundary,false);
frontImage.CustomizeColor(0, 0, 0, 255, Color.GREEN, true);
frontImage.Visualize(sparkContext, queryRDD);
/*---------------------------- Step 4: Use Babylon Overlay Operator: Choropleth Map (back) and Scatter Plot (front) ----------------------------*/
OverlayOperator overlayOperator = new OverlayOperator(visualizationOperator.pixelImage);
overlayOperator.JoinImage(frontImage.pixelImage);
/*---------------------------- Step 5: Generate final image ----------------------------*/
NativeJavaImageGenerator imageGenerator = new NativeJavaImageGenerator();
imageGenerator.SaveAsFile(overlayOperator.backImage, outputPath, ImageType.PNG);