; create-contrast-mask.scm version 1
; 06 July 2006
; A Script-Fu script to correct the exposure of dark areas
; without overexposing bright areas

; 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.

; Only tested on v2.2.11


(define (script-fu-contrast img drawable gblur opacity-mask)

	(gimp-undo-push-group-start img)

	; Copy image, add as new layer, set mode to hue
	(set! hue (car (gimp-layer-copy drawable 1)))
	(gimp-image-add-layer img hue -1)
	(gimp-layer-set-name hue "hue")
	(gimp-layer-set-mode hue HUE)

	; Copy image, add as new layer, set mode to saturation
	(set! saturation (car (gimp-layer-copy drawable 1)))
	(gimp-image-add-layer img saturation -1)
	(gimp-layer-set-name saturation "saturation")
	(gimp-layer-set-mode saturation SATURATION)

	; Copy image, add as new layer
	(set! contrast (car (gimp-layer-copy drawable 1)))
	(gimp-image-add-layer img contrast -1)
	(gimp-layer-set-name contrast "contrast")

	; Desaturate, invert, gaussian-blur, set opacity, set mode to overlay
	(gimp-desaturate contrast)
	(gimp-invert contrast)
	(plug-in-gauss-iir 1 img contrast gblur 1 1)
	(gimp-layer-set-opacity contrast opacity-mask)
	(gimp-layer-set-mode contrast OVERLAY)

	; Cleanup
	(gimp-undo-push-group-end img)
	(gimp-displays-flush)
)

(script-fu-register "script-fu-contrast"
		_"<Image>/Script-F_u/_Underwater Photos/_Contrast Overlay"
		"Create a contrast layer with hue and saturation copies of original image"
		"www.tankedup-imaging.com"
		"Tanked Up Underwater Imaging"
		"06 July 2006"
		""
		SF-IMAGE "Image" 0
		SF-DRAWABLE "Drawable" 0
		SF-ADJUSTMENT   _"Blur Radius" '(20 1 200 1 1 1 0 1)
		SF-ADJUSTMENT "Opacity" '(80 0 100 1 20 0 0)
)