d3.interpolateRgbBasis()

d3.interpolateRgbBasis(colors)

Returns a uniform nonrational B-spline interpolator through the specified array of colors, which are converted to RGB color space. Implicit control points are generated such that the interpolator returns colors[0] at t = 0 and colors[colors.length - 1] at t = 1. Opacity interpolation is not currently supported. See also d3.interpolateBasis, and see d3-scale-chromatic for examples.