; filtre-diffuseur.scm
; by Antoine Tissier 
; http://antoine.tissier.lost-oasis.net/gimp/

; Version 0.3 (20030928) 

; Description
;
; This 'script-fu' fakes a diffusion filter.
;
; Changelog
; 0.2->0.3 :
;	the intensity parameter has been added
;	the layers are now renamed
;	an intensity mask has been added
;	comments added
; 0.1->0.2 : 
; 	english translation
; 	the level parametre has been added
; 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 (photo-diffusion_filter image drawable levels radius intensity negative)
	(let* (
		(width (car (gimp-image-width image))) 
		(height (car (gimp-image-height image)))
		(blur_layer  (car (gimp-image-get-active-layer image)))
		(old_fg_color (car (gimp-palette-get-foreground)))
		(old_bg_color (car (gimp-palette-get-background)))
		(grey_color (/ (* (abs (- 100 intensity)) 255) 100)))
		
	(gimp-undo-push-group-start image)
	
	;duplication of the background layer
	(gimp-selection-all image)
	(gimp-edit-copy drawable)
	(let ((floating-sel (car (gimp-edit-paste drawable FALSE))))
	(gimp-floating-sel-to-layer floating-sel))
	
	;the foreground layer mode is changed
	(let ((orig_layer (car (gimp-image-get-active-layer image))))
	(gimp-layer-set-name orig_layer "original")
	
	(if (= negative FALSE)
		(gimp-layer-set-mode orig_layer OVERLAY-MODE))
	
	(if (= negative TRUE)
		(gimp-layer-set-mode orig_layer MULTIPLY-MODE))	
	
	;duplication of the foreground layer
	(let ((floating-sel (car (gimp-edit-paste drawable FALSE))))
	(gimp-floating-sel-to-layer floating-sel))
	(let ((inte_layer (car (gimp-image-get-active-layer image))))
	(gimp-layer-set-name inte_layer "intensity")
	(gimp-layer-set-mode inte_layer NORMAL-MODE)
	
	;creation of the intensity mask
	;(it is better to create an editable mask than just using opacity )
	(gimp-palette-set-background (list grey_color grey_color grey_color))
	(let ((inte_mask (car (gimp-layer-create-mask inte_layer 0))))
	(gimp-image-add-layer-mask image inte_layer inte_mask)
	(gimp-edit-fill inte_mask BG-IMAGE-FILL)
	
	;the background layer is blurred and brigthened
	(gimp-layer-set-visible orig_layer FALSE)
	(gimp-layer-set-visible inte_layer FALSE)
	(gimp-image-set-active-layer image blur_layer)
	(plug-in-gauss-iir2 TRUE image drawable radius radius)
	(gimp-levels drawable 0 0 255 levels 0 255)
	(gimp-layer-set-name blur_layer "blur")

	(gimp-layer-set-visible orig_layer TRUE)
	(gimp-layer-set-visible inte_layer TRUE)
	(gimp-palette-set-background old_bg_color)
	(gimp-palette-set-foreground old_fg_color)
	(gimp-undo-push-group-end image)
	(gimp-displays-flush)))))
)

(script-fu-register "photo-diffusion_filter" 
								"<Image>/Script-Fu/Photo/Diffusion filter..."
								"Fakes a diffusion filter"
								"Antoine Tissier"
								"Antoine Tissier"
								"September 2003"
								"RGB RGBA GRAY GRAYA"
								SF-IMAGE "Image" 0
								SF-DRAWABLE "Drawable" 0 
								SF-ADJUSTMENT "Levels" '(1.5  0.1  10   1  10   1   0)
								SF-ADJUSTMENT "Radius" '( 15    1 100   1   1   0   0)
								SF-ADJUSTMENT "Intensity" '(75  1 100   1   1   0   0)
								SF-TOGGLE "Negative" FALSE )