; tapered_stroke_along_path.scm
; by Rob Antonishen
; http://ffaat.pointclark.net

; Version 1.0 (20080926)

; Description
;
; paints a tapered stroke along the path
;

; License:
;
; This program is free software; you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation; either version 2 of the License, or
; (at your option) any later version. 
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
; GNU General Public License for more details.
;
; The GNU Public License is available at
; http://www.gnu.org/copyleft/gpl.html

(define (tapered_stroke_along_path img inLayer inPath inStartWidth inEndWidth inSpacing inCurve)

  (let*
    (
	  (width (car (gimp-image-width img)))
	  (height (car (gimp-image-height img)))
	  (brushTemp 0)
	  (varRadius (/ inStartWidth 2.0))
	  (varFirstStroke (aref (cadr (gimp-vectors-get-strokes inPath)) 0))
	  (varPathLength (car (gimp-vectors-stroke-get-length inPath varFirstStroke 1)))
	  (varCounter 0)
      (*newpoint* (cons-array 2 'double))
	  (varTemp 0)
	  (varRepaint 0)
    )
    ;  it begins here
    (gimp-context-push)
    (gimp-image-undo-group-start img)

	;logging
	;(gimp-message-set-handler ERROR-CONSOLE)
    ;(gimp-message-set-handler CONSOLE)
    ;(gimp-message-set-handler MESSAGE-BOX)
	;or start GIMP wwith "gimp --console-messages" to spawn a console box
	;then use this:
	;(gimp-message "foobar") 

	;testing for functions defined
	;(if (defined? 'plug-in-shift) (gimp-message "It Exists") (gimp-message "Doesnt Exist"))

	;Uses: 
	;gimp-vectors-stroke-get-point-at-dist
	;gimp-vectors-stroke-get-length
	;
				
    ;Set up Brush	
    (set! brushTemp (car (gimp-brush-new "TaperedStrokeBrush")))
	(gimp-brush-set-shape brushTemp BRUSH-GENERATED-CIRCLE)
    (gimp-brush-set-hardness brushTemp 1)
    (gimp-brush-set-radius brushTemp varRadius)
    (gimp-brush-set-spacing brushTemp inSpacing)
    (gimp-brush-set-spikes brushTemp 2)
    (gimp-brush-set-aspect-ratio brushTemp 1)
    (gimp-brush-set-angle brushTemp 0)
	(gimp-context-set-brush brushTemp)
			
	;walk the path
	(while (<= varCounter varPathLength)
	   (set! varTemp (gimp-vectors-stroke-get-point-at-dist inPath varFirstStroke varCounter 1))
	   
	   (if (and (<> (list-ref varTemp 0) 0) (<> (list-ref varTemp 1) 0))
         (begin
	       (aset *newpoint* 0 (list-ref varTemp 0))   ; set the paint array
	       (aset *newpoint* 1 (list-ref varTemp 1))
	       (gimp-paintbrush-default inLayer 2 *newpoint*) ; paint point with paintbrush
	   	  )
	   )
	   (set! varCounter (+ varCounter (* 0.02 varRadius inSpacing))) ; 0.02 is 2/100 to turn the inSpacing to a percent
	   (set! varRadius (/ (+ (* (pow (/ varCounter varPathLength) inCurve) (- inEndWidth inStartWidth)) inStartWidth) 2.0))
	   (set! varRepaint (+ varRepaint 1))
	   (if (> varRepaint 25)
	     (begin
		   (set! varRepaint 0)
           (gimp-displays-flush)
		   (gimp-progress-update  (/ varCounter varPathLength))
		 )
	   )   
       (gimp-brush-set-radius brushTemp varRadius)	   

    )
	
	(gimp-brush-delete brushTemp)
	;done
	(gimp-image-undo-group-end img)
	(gimp-progress-end)
	(gimp-displays-flush)
	(gimp-context-pop)
  )
)

(script-fu-register "tapered_stroke_along_path"
        		    "<Image>/Edit/Tapered Stroke Path..."
                    "Paint a Tapering Stroke Along the Path in the Current Colour"
                    "Rob Antonishen"
                    "Rob Antonishen"
                    "Sept 2008"
                    "RGB* GRAY*"
                    SF-IMAGE      "image"      0
                    SF-DRAWABLE   "drawable"   0
                    SF-VECTORS    "Path to Stroke" -1
                    SF-ADJUSTMENT "Stroke Start Width" (list 20 0.2 100 1 10 1 SF-SLIDER)					
                    SF-ADJUSTMENT "Stroke End Width" (list 1.0 0.2 200 1 10 1 SF-SLIDER)					
                    SF-ADJUSTMENT "Brush Spacing" (list 20 0.1 200 1 10 1 SF-SLIDER)	
                    SF-ADJUSTMENT "Taper Exponent (1=linear)"    (list 5 0.2 10 1 1 1 SF-SPINNER)
)