If you are using Script-fu and your script is for versions 2.2.x of the
GIMP then the following function will return the length of a given path.
It will work with version 2.3 but will generate some deprecation
warnings (and 2.3 provides better methods).

## Advertising

;; 'sflib-path-get-length' returns the length of the specified path
;;
;; NOTE: If the end of the path is a X=0, Y=0 (and the slope
;; is zero there) then the value returned will be
;; slightly shorter (as much as 1.4) than actual.
;; (The path may *start* at 0,0)
(define (sflib-path-get-length image pathname)
(let* (
(path (gimp-path-get-points image pathname))
(last-index (* 9 (- (trunc (/ (+ (caddr path) 3) 9)) 1)))
(points (cadr (cddr path)))
(point-guess)
(point-lo (list (aref points 0) (aref points 1)))
(point-hi (list (aref points last-index) (aref points (+
last-index 1))))
(guess (sqrt (+ (* (- (car point-hi) (car point-lo))
(- (car point-hi) (car point-lo)))
(* (- (cadr point-hi) (cadr point-lo))
(- (cadr point-hi) (cadr point-lo)))))
)
(guess-lo 0)
(guess-hi (* guess 2))
(Done FALSE)
(pnt (gimp-path-get-point-at-dist image guess-hi))
)
(while (not (and (= (car pnt) 0) (= (cadr pnt) 0) (= (caddr pnt) 0)))
(set! guess-hi (* guess-hi 2))
(set! pnt (gimp-path-get-point-at-dist image guess-hi))
)
(while (= Done FALSE)
(set! point-guess (gimp-path-get-point-at-dist image guess))
(if (and (= (car point-guess) 0) (= (cadr point-guess) 0) (=
(caddr point-guess) 0))
(begin
(set! point-hi point-guess)
(set! guess-hi guess)
(set! guess (/ (+ guess guess-lo) 2))
)
(if (or (and (= (car point-guess) (car point-lo))
(= (cadr point-guess) (cadr point-lo))
)
(and (= (car point-guess) (car point-hi))
(= (cadr point-guess) (cadr point-hi))
))
(set! Done TRUE)
(begin
(set! point-lo point-guess)
(set! guess-lo guess)
(set! guess (/ (+ guess guess-hi) 2))
)
)
)
)
guess
)
)
--
Paolo Herms
Sun, 24 Sep 2006 07:52:03 -0700
> Hello,
> I've got a cartographic image and I designed a path on it.
> Is there any way to find out its length?
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