I thought it would be nice to create heatmaps from the Openstreetmap data (i.e. for displaying the areas lacking « addr:housenumber »). I created, OsmosisHeatmap (jar file, source), a plug-in for Osmosis (a command line tool for processing Openstreetmap data) that generates a JavaScript file with the coordinates, JS that can be used by the sample HTML page based on Leaflet and Leallet.Heat.
And it gives something like that:
![A plan of a part of Paris in OpenStreetMap default style, covered by a layer of heatmap](https://fabsk.eu/blog/wp-content/uploads/2016/05/sample.jpg)