RasterColorizer support

[eightysteele]

Hey Guys, just wondering what it would take to fold in RasterColorizer support into mapnik-jni? cc: @springmeyer

[springmeyer]

Explain more what you'd like to do. Proper bindings for RasterColorizer are not trivial to expose. A shortcut would be to load an XML that contained an empty map and a style with a RasterColorizer, then complete the map programmatically in java.

[eightysteele]

We'd like to build a map tiler for big raster data that rides on Mapnik-jni, and we want it to support dynamic styling by passing in a carto raster symbolizer. Something like:

/tiles/x/y/z.png?carto={raster-symbolizer}

For this to work, do you think proper bindings are the right tool for the job, or is the shortcut the best way to get started here?

[springmeyer]

shortcut should get you started. For now you could just pass the XML on the url. Carto would of course be nice, but since the main carto impl is in javascript I assume you can't easily hook into that from java.

[eightysteele]

I'll see how far I can get with XML and Java. On the other hand, there is Rhino of course.

[springmeyer]

@eightysteele - how did this go working around it for the time being?

[eightysteele]

@springmeyer we tested and the workaround is gold. we didn't try the rhino route though which would be interesting for hooking into the main carto implementation in js.

[springmeyer]

btw, carto now supports raster-colorizer: mapbox/carto#5