color wheel in gimp method?

[denzjos]

(03-15-2020, 10:53 AM)Ofnuts Wrote:

(03-14-2020, 02:38 PM)denzjos Wrote: Sorry about that, it seems that the angle from the first line is not known in the Ofnuts plugin.
I don't know if Ofnuts has an explanation about that?

About what?

Sorry about that I posted a wrong solution for this item.
Question to Ofnuts if there is an explanation (or solution) for the first line that has the wrong angle (it don't go through the center point, all the orther lines go through the center)

[Ofnuts]

At least two reasons:

1) the first point may not be the one you think:

   

2) The "circle" is not a circle, it is an approximation of a circle. Creating the circle as a path directly (using the various scripts available) makes it a fairly clean (if not perfect) circle, but creating a path from a circular selection makes it even less a circle so there is no guarantee that the local tangent is perpendicular to a line that goes from that point to the (assumed) center if the "circle".

[denzjos]

Ofnuts,  that is a very correct mathematical explanation and now I understand how I can use the plugin. I tested it and made a circle path (Script-Fu / Shape Paths / Circle) and now my workflow gives a correct result. Thank you for the complete explanation. 

1/ draw a circle path
2/ on gimp menu : Select / To Path
3/ draw a straight vertical line  (lenght diameter circle)
4/ select the line (Fuzzy Select tool)
5/ on gimp menu : Edit / copy
6/ on gimp menu : Select / None
7/ on gimp menu : Edit / Brush strokes on path (value 9 in your case)
8/ clean up the rays outside the circle
9/ color the sections ( fuzzy select section/ fill section with color 'Bucket Fill Tool')

   

[Ofnuts]

With ofn-path-to-shape:

1. You create a path which is a single segment
   
2. There is a function to create spokes from the segment
   
3. There is a function to create a circle from the segment
   
4. You stroke the two paths
   

   

[Ofnuts]

Another method not mentioned

1. Create a gradient with 9 bars
   
2. Create a circle selection
   
3. Use the blend tool for a conical-asymmetric blend