Feature request: more interpolations schemes

[briochemc]

Not sure how to title this issue, but I think it would be nice if one could use different interpolation schemes between colors.

I'm bringing up this issue following JuliaGraphics/ColorSchemes.jl#60, which is about adding bipolar colormaps. In particular, the referenced matplotlib tool, https://github.com/endolith/bipolar-colormap, proposes colormaps designed along Bézier curves in colorspace (instead of piece-wise linear interpolations). Not sure this would be possible but that would be one part of this feature request.

Otherwise, I thought it might be possible to use some of Interpolations.jl, e.g., B-splines, and so on.

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EDIT: Of course, maybe none of this makes sense, so if that's the case sorry for the noise and please don't hesitate to close right away.

[cormullion]

Good idea!

Doing Bezier interpolation through RGB space is definitely too difficult for me to add (I only just managed to add simple linear interpolations), but if someone wants to write it, it would be useful, I think.