for the final daw of my series, i created a tool that imports both the vector
data of a line drawing (tracing that i made) and the RGB values
of the original image. It then draws the tracing and uses the RGB
values to adjust the width of the stroke.
In the second and third examples i also used the color data from
the original picture to adjust the line color as well. All of this
is pretty lo-fi, i'm only using values from a 200x200 image, and
only taking a point sample (rather than averaging the value across
the entire length of the line).
I'm pretty happy with the third drawing, at least in the sense
that it has a bit more pencil-like quality to it.
here is a link to the file that created it.
i ghosted the original image behind it so you have some frame of