Philippe Rivière

Thanks for the report. Yes, we would want to implement this — contributions are welcome.

It seems 2 to 3 times slower https://observablehq.com/@fil/interpolate-colors-with-catmull-rom#speedtest ; lab maybe a bit slower than rgb, but it's not a huge impact. And I haven't yet looked at the catmull-rom...

I've updated my notebook with a lab monotone; the difference is a little perceptible with the Set or Paired color schemes, but there is no way to say that one...

I've tightened up the implementation, and labMonotone is now even faster than the baseline "rgbbasis" (if you discount lab.toString(), which is now the bottleneck).

Added rgbmonotone. I don't have a strong opinion on which one should be the default, everything works globally fine and quickly.

EDIT: as I was implementing unit tests I realized that the function I used was not monotone but just cubic. It seems good enough for our purposes, but we shouldn't...

Since this is just a *default*, and the various options (among the best) are almost indistinguishable, my intention at this point is to implement the fastest of them, ie **monotone...

It might be too disruptive for the case of lines—adding a feature at the expense of clarity (like, a good error message when people forget to specify x or y)....

Is this maybe linked to note 8 of the README ([introduced here](https://github.com/d3/d3-zoom/commit/c52ecb08cbdc193e403f050a62ed37fcd2d1ac39))?

More remarks after a first (failed) attempt: ### scatterplot example: - for the wheel input: - changing the center should only be done once at the start of the gesture—otherwise...