Leland Brown's Texture Shading

[waldronate]

I finally got around to implementing Leland Brown's Texture Shading algorithm ( http://www.textureshading.com/Home.html for information ). It's an interesting result, especially compared to other items in the Wilbur shader library.

[su_liam]

This gonna be in the next Wilbur release?

[waldronate]

Sure. Should be up now.

Note that I chopped the available parameters so that there isn't the scale-dependence in the original shader (that is, there is no assumption about the units of the bounds of the map area).