Add slope algorithm

[tayden]

Wondering if it would be valuable to add a slope algorithm for tile requests? This seems like it would be a common enough need to include it as a default DEM algorithm, rather than let people implement themselves.

I'm happy to create a PR to do this, if it makes sense. I'm slightly uncertain if it makes the most sense to return data in the range [0,1] (i.e. percent slope), or to rescale it to [0,255] and return byte values.

For parameters, I think buffer would be required to help with edge artifacts. Additionally, a scale exaggeration parameter would likely be useful, as well as min_slope (defaulting to 0) and max_slope (defaulting to 1) that can be used to rescale and clip the output values for visualization purposes.

[vincentsarago]

👍

I'm happy to create a PR to do this, if it makes sense. I'm slightly uncertain if it makes the most sense to return data in the range [0,1] (i.e. percent slope), or to rescale it to [0,255] and return byte values.

You can return value from 0 to 1 and then let the user deside what to do

Happy to review any PR 🙏

[tayden]

Excellent! Done (I think?) #1088