Fun (continuous) thread all 
Kangaroo’s ImageCircles component takes a coloured mesh as input, which can be something 3 dimensional, so can be used for this:
colour_curve.gh (116.8 KB)
This one starts with all the points existing from the beginning, and gradually increases the radius multiplier. More efficient is to start with only a few points and divide curves when they get above a certain length, but that currently needs to be scripted like shown in this example.
I can make another example showing how to combine the image based sizing with this iterative line splitting if it would be of interest.
In a different direction, I also played a little recently with another way of making shaded images from a continuous line, but by adjusting tension in a grid-
I’ll post the script for this one too soon.