decode LERC tiles from Esri ImageServer to draw in Leaflet

investigate how much work would be necessary to refactor/extend imageMapLayer to take advantage of tile caches when they are present.

http://elevation3d.arcgis.com/arcgis/rest/services/WorldElevation3D/Terrain3D/ImageServer

in the case of Esri’s recent work to open source LERC, it would be really cool if we could download/decode and draw them in Leaflet.

cc/ @tomwayson

[jwasilgeo]

Here’s a working sample and brief write-up: https://github.com/jwasilgeo/leaflet-experiments#lerc-imagery-land-cover-layer

Happy to discuss the code a bit more. It is based on the LeafletJS GridLayer approach pioneered by @jgravois but customized for this particular land cover ImageServer: https://github.com/jwasilgeo/leaflet-experiments/blob/master/lerc-landcover/script.js#L4

Between this and @jgravois’s https://github.com/jgravois/lerc-leaflet/, we might have some good ideas coalescing to see if/how to bring this into the esri-leaflet ecosystem. I’ll write up some more thoughts later.

[jwasilgeo]

@aaronkyle here is a screenshot to provide hope. 😃 The approach is as expected: use a Leaflet map in WGS84, and for the layer itself manually decode pixels from each tile and write them into a 2d image canvas with appropriate RGB values. This was inspired by @jgravois’s https://github.com/jgravois/lerc-leaflet but customized for this particular landcover service.

I’d like to first clean up the code before sharing, but I hope to have something to show soon in the coming days.