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Script-fu example 06: Creating a function to draw lines, using it to draw stars

Creates a 250x250 picture and draws a star into it.
Since I am going to draw several lines here, I create a function that takes care of drawing a line.
draw_line.scm
(define (draw-line layer x-from y-from x-to y-to) 
  (let* (
          (points (cons-array 4 'double))
        )

        (aset points 0 x-from)
        (aset points 1 y-from)
        (aset points 2 x-to  )
        (aset points 3 y-to  )

        (gimp-pencil layer 4 points)
  )
)
The function is then called in the following script.
ex_06.scm
(define (ex_06 nof-points jump-points) 

  (
     (let* (
             (my-image (car (gimp-image-new 250 250 RGB)))

             (my-layer (car (gimp-layer-new my-image 250 250 RGB-IMAGE "my layer" 0 NORMAL)))

             (i nof-points)

           )

       (gimp-image-add-layer my-image my-layer 0)

       (gimp-context-set-background '(255 255 255))
       (gimp-context-set-foreground '(000 000 000))

       (gimp-drawable-fill my-layer BACKGROUND-FILL)
       
       (gimp-brushes-set-brush "Circle (01)"    )   
       (gimp-brush-set-spacing "Circle (01)" 100)        

       (while (> i 0)

         (draw-line 
            my-layer 
            (+ 125 (* 100 (sin (* 2 *pi* jump-points    i    (/ 1 nof-points)))))
            (+ 125 (* 100 (cos (* 2 *pi* jump-points    i    (/ 1 nof-points)))))
            (+ 125 (* 100 (sin (* 2 *pi* jump-points (+ i 1) (/ 1 nof-points)))))
            (+ 125 (* 100 (cos (* 2 *pi* jump-points (+ i 1) (/ 1 nof-points)))))
         )

         (set! i (- i 1))
       )

       (gimp-file-save RUN-NONINTERACTIVE my-image my-layer "c:\\temp\\ex_06.jpg" "")

     )
  )
)

c:\> start gimp-2.2.exe -d -i -b  "(ex_06 10 3)" "(gimp-quit 0)"
See also other examples