; The GIMP -- an image manipulation program
; Copyright (C) 1995 Spencer Kimball and Peter Mattis
; 
; Lava effect
; Copyright (c) 1997 Adrian Likins
; aklikins@eos.ncsu.edu
;
; based on a idea by Sven Riedel <lynx@heim8.tu-clausthal.de>
; tweaked a little by Sven Neumann <neumanns@uni-duesseldorf.de>
;
; 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.
; 
; You should have received a copy of the GNU General Public License
; along with this program; if not, write to the Free Software
; Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

(define (rand-num )
   (srand (realtime))
   (/ (rand 10) 10))
   

(define (set-pt a index x y)
  (prog1
   (aset a (* index 2) x)
   (aset a (+ (* index 2) 1) y)))


(define (spline-shag-it)
  (let* ((a (cons-array 18 'byte)))
    (set-pt a 0 0 0)
    (set-pt a 1 31 235)
    (set-pt a 2 63 23)
    (set-pt a 3 95 230)
    0(set-pt a 4 127 25)
    (set-pt a 5 159 21)
    (set-pt a 6 191 200)
    (set-pt a 7 223 24)
    (set-pt a 8 255 255)
    a))


(define (script-fu-shag image
			drawable
			random-values
			redx
			redy
			greenx
			greeny
			bluex
			bluey
			keep-selection
			seperate-layer)
  (let* (
	 (type (car (gimp-drawable-type-with-alpha drawable)))
	 (image-width (car (gimp-image-width image)))
	 (image-height (car (gimp-image-height image)))
	 (old-bg (car (gimp-palette-get-background))))

    (srand (realtime))
    (gimp-image-disable-undo image)
    (gimp-layer-add-alpha drawable)
    
    (if (= (car (gimp-selection-is-empty image)) TRUE)
	(begin
	  (gimp-selection-layer-alpha image drawable)
	  (set! active-selection (car (gimp-selection-save image)))
	  (set! from-selection FALSE))
	(begin 
	  (set! from-selection TRUE)
	  (set! active-selection (car (gimp-selection-save image)))))
    
    (set! selection-bounds (gimp-selection-bounds image))
    (set! select-offset-x (cadr selection-bounds))
    (set! select-offset-y (caddr selection-bounds))
    (set! select-width (- (cadr (cddr selection-bounds)) select-offset-x))
    (set! select-height (- (caddr (cddr selection-bounds)) select-offset-y))
    
    (if (= seperate-layer TRUE)
	(begin
	  (set! shag-layer (car (gimp-layer-new image 
						select-width 
						select-height 
						type 
						"Shag Layer" 
						100 
						NORMAL)))
	  
	  (gimp-layer-set-offsets shag-layer select-offset-x select-offset-y)
	  (gimp-image-add-layer image shag-layer -1)
	  (gimp-selection-none image)
	  (gimp-edit-clear image shag-layer)
	  
	  (gimp-selection-load image active-selection)
	  (gimp-image-set-active-layer image shag-layer))) 
    
    (set! active-layer (car (gimp-image-get-active-layer image)))
    
    (if (= random-values TRUE)
	(begin
	  (plug-in-harmonic 1 image active-layer 
			 (/ (rand 100) 100)
			 (/ (rand 100) 100)
			 (/ (rand 100) 100)
			 (/ (rand 100) 100)
			 (/ (rand 100) 100)
			 (/ (rand 100) 100)))
	  (plug-in-harmonic 1 image active-layer redx redy greenx greeny bluex bluey))

    (gimp-curves-spline image active-layer 0 18 (spline-shag-it))
    (gimp-brightness-contrast image active-layer 0 127)
    

    (if (= keep-selection FALSE)
	(gimp-selection-none image))
   
    (gimp-image-set-active-layer image drawable)
    (gimp-image-remove-channel image active-selection)
    (gimp-image-enable-undo image)
    (gimp-displays-flush)))

(script-fu-register "script-fu-shag"
		    "<Image>/Script-Fu/Decor/Shagadelic"
		    "Generates shagadelic patterns. Groovy, baby!."
		    "Adrian Likins <adrian@gimp.org>"
		    "Adrian Likins"
		    "10/12/97"
		    "RGB RGBA GRAY GRAYA"
		    SF-IMAGE "Image" 0
		    SF-DRAWABLE "Drawable" 0
		    SF-TOGGLE "Random values?" TRUE
		    SF-VALUE "Red X" ".25"
		    SF-VALUE "Red Y" ".40"
		    SF-VALUE "Green X" ".89"
		    SF-VALUE "Green Y" ".33"
		    SF-VALUE "Blue X" ".10"
		    SF-VALUE "Blue Y" ".75"
		    SF-TOGGLE "Keep Selection?" TRUE
		    SF-TOGGLE "Seperate Layer?" TRUE)