new leaflet sample [work in progress]

[jgravois]

work in progress (toward #3)

• do something to account for 257x257px tiles?
• standardize color ramp displayed for individual tiles
• get rid of white band at international dateline
• figure out how to dig into the actual elevation value to display a value on mousemove
• repackage code as a custom Leaflet layer?

[jgravois]

@lucianpls i just layed down another commit so the sample now digs elevation values out of the data directly. (its based on the tutorial here).

the next step is to define a static range/colormap for all tiles...

[jgravois]

getting closer...

[lucianpls]

What you display now is the value of the pixel, not the elevation. You can't interrogate the canvas for that, you have to get the corresponding value from the decoded LERC array.

[lucianpls]

@jgravois
There will be cases where the LERC layer will be an overlay on top of a basemap. Then the NoData areas should be transparent so that the basemap will be seen.

[lucianpls]

@jgravois
The white edge (left and top too) is a known issue, in the tiles themselves. Those pixels are flagged by the mask as NoData.

[jgravois]

alright, i pushed a few more commits, cleaned up the white border and made min/max values configurable via user input.

if anyone can help with figuring out how to dig out the elevation data every time the mouse is moved, that would be really sweet.

[patrickarlt]

@lucianpls now that we have #5 done how would we convert a x/y pixel position on the tile to a value from the decoded array?

[lucianpls]

I got it working, but sometimes it says "undefined", not sure why.