Get maximum and minimum values within current view

Hi there,

I've got your library going on the https://hirdsexplorer.nz/ website, and it's worked quite well so far.

I'd like to be able to update the colormap after every scroll event, so that it spans from the lowest to the highest values **that are currently visible**, to allow the user to see the spatial variation in that particular area. This is a common feature in GIS software packages. At the moment I use a global minimum and maximum on each colormap, and the maximum is dictated by the mountains.

Is this a feature that you would be willing to have in your library?

I would be willing to help in some way, but I'm not sure how. I've had a look in src/shaders/index.ts to see how pixel values are calculated, but it seems to me the challenge will be in working out which parts of each tile is visible at any one time. Do you have any ideas on how it could be done?

Thanks, Cameron

Start by reviewing src/shaders/index.ts and the existing scroll-event and tile-rendering flow. Determine how the currently visible parts of tiles could provide minimum and maximum values for the colormap. Done means the colormap updates after scrolling and spans the lowest and highest values visible in the current view.

Written by the indexing model from the issue text.