I don't know if this is the right list but how do you change the Value (HSV) of a color in script-fu.

I am playing with the sphere script. And I would like to change the lighting intensity.

Example:
Color (255 0 0)
I want a new color as if the only the value had been changed to like 50, so then the new color would be (128 0 0). Thanks in advance.

Figured it out! Here is the semifinished script.

; Create a 3D sphere with optional shadow ; The sphere's principle color will be the foreground ; Parameters:
; bg-color: background color
; sphere-color: color of sphere
; radius: radius of the sphere in pixels ; light: angle of light source in degrees ; shadow: whather to create a shadow as well

(define (script-fu-sphere-plus radius light
light-position
light-intensity
shadow
bg-color
sphere-color
keep-selection)
(let* ((width (* radius 3.75))
(height (* radius 2.5))
(img (car (gimp-image-new width height RGB))) (drawable (car (gimp-layer-new img width height RGB-IMAGE "Sphere Layer" 100 NORMAL-MODE))) (radians (/ (* light *pi*) 180))
(cx (/ width 2))
(cy (/ height 2))
(light-x (+ cx (* radius (* light-position (cos radians))))) (light-y (- cy (* radius (* light-position (sin radians))))) (light-end-x (+ cx (* radius (cos (+ *pi* radians))))) (light-end-y (- cy (* radius (sin (+ *pi* radians))))) (offset (* radius 0.1)))

(gimp-context-push)

(gimp-image-undo-disable img) (gimp-image-add-layer img drawable 0) (gimp-context-set-foreground sphere-color) (gimp-context-set-background bg-color) (gimp-edit-fill drawable BACKGROUND-FILL)

(set! light-i (list (* (car sphere-color) light-intensity) (* (cadr sphere-color) light-intensity) (* (caddr sphere-color) light-intensity) )) (gimp-context-set-background light-i)

(if (and (or (and (>= light 45) (= light 105))) (= shadow TRUE))
(let ((shadow-w (* (* radius 2.5) (cos (+ *pi* radians)))) (shadow-h (* radius 0.5))
(shadow-x cx)
(shadow-y (+ cy (* radius 0.65)))) (if (< shadow-w 0)
(prog1 (set! shadow-x (+ cx shadow-w)) (set! shadow-w (- shadow-w))))

(gimp-ellipse-select img shadow-x shadow-y shadow-w shadow-h CHANNEL-OP-REPLACE TRUE TRUE 7.5) (gimp-edit-bucket-fill drawable BG-BUCKET-FILL MULTIPLY-MODE 100 0 FALSE 0 0)))

(gimp-ellipse-select img (- cx radius) (- cy radius) (* 2 radius) (* 2 radius) CHANNEL-OP-REPLACE TRUE FALSE 0)

(gimp-edit-blend drawable FG-BG-RGB-MODE NORMAL-MODE GRADIENT-RADIAL 100 offset REPEAT-NONE FALSE FALSE 0 0 TRUE
light-x light-y light-end-x light-end-y)

(if (= keep-selection FALSE) (gimp-selection-none img)) (gimp-image-undo-enable img)
(gimp-display-new img)

(gimp-context-pop)))

(script-fu-register "script-fu-sphere-plus" _"_Sphere Plus..."
"Simple sphere with a drop shadow" "Spencer Kimball, Nolan Clayton" ""
"1996, 2005"
""
SF-ADJUSTMENT _"Radius (pixels)" '(100 5 500 1 10 0 1)
SF-ADJUSTMENT _"Lighting (degrees)" '(45 0 360 1 10 0 0)
SF-ADJUSTMENT _"Lighting (position)" '(0 0 1 .2 1 1 0)
SF-ADJUSTMENT _"Lighting (intensity)" '(0 0 1 .1 1 1 0)
SF-TOGGLE _"Shadow" TRUE SF-COLOR _"Background color" '(255 255 255) SF-COLOR _"Sphere color" '(255 0 0) SF-TOGGLE _"Keep Selection" TRUE )

(script-fu-menu-register "script-fu-sphere-plus" _"/Xtns/Script-Fu/Misc")

HSV
In case anyone didn't get this. Here is how I changed the value of a color in script-fu. You could do something similar for Saturation and I guess hue, not sure though it would create the desired effect if you played with the hue.

;;sphere-color is a color ;;light-i will be the new color
;;light-intensity is the new value (HSV)

(set! light-i (list (* (car sphere-color) light-intensity) ;;Red (* (cadr sphere-color) light-intensity) ;;Green (* (caddr sphere-color) light-intensity) )) ;;Blue (gimp-context-set-background light-i)