  PS - style Gradient Map 
  by   
  Based on a tutorial found on the GimpTalk.com forums : 
; -style-gradient-map-for-GIMP-5750-1.html  
; Seemed easy enough to convert into a plug-in, so I did
; The script is located in menu "<Image> / Script-Fu / Artistic / PS Gradient Map..."
;
  Last changed : 17 June 2008 
;
  Copyright ( C ) 2008   
;
; --------------------------------------------------------------------
;  
; Changelog:
   Version 0.1 
;    - Initial plug-in script
;
; --------------------------------------------------------------------
;
; 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 3 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, you can view the GNU General Public
  License version 3 at the web site -3.0.html 
  Alternatively you can write to the Free Software Foundation , Inc. , 675 Mass 
  Ave , Cambridge ,   , USA . 

(define (script-fu-ps-gradmap theImage theLayer gradStart gradEnd opacityLevel flattenImage?)

    (let* 
	    (
			(workLayer (car (gimp-layer-copy theLayer 0)))
			;Save the original foreground and background colors
			(orgFGColor (car (gimp-context-get-foreground)))
			(orgBGColor (car (gimp-context-get-background)))
	    )

Start an undo group so the process can be undone with one undo 
	    (gimp-image-undo-group-start theImage)

	    ;Select none
	    (gimp-selection-none theImage)

	    ;Add the duplicate layer to the image
	    (gimp-image-add-layer theImage workLayer 0)

	    ;Rename the layer
	    (gimp-drawable-set-name workLayer "Work Layer")

		;Desaturate the layer
		(gimp-desaturate workLayer)

Set the foreground color to gradStart 
		(gimp-context-set-foreground gradStart)

		;Set the background color to gradEnd)
		(gimp-context-set-background gradEnd)

		;Run the gradient color map
		(plug-in-gradmap 1 theImage workLayer)

Set the layer mode to COLOR - MODE ( 13 ) 
		(gimp-layer-set-mode workLayer COLOR-MODE)

		;Set the opacity level
		(gimp-layer-set-opacity workLayer opacityLevel)

		(if (eqv? flattenImage? TRUE)
			(gimp-image-flatten theImage)
		)

		;Set the foreground and background colors back to their originals
		(gimp-context-set-background orgBGColor)
		(gimp-context-set-foreground orgFGColor)

	    ;Finish the undo group for the process
	    (gimp-image-undo-group-end theImage)

	    ;Ensure the updated image is displayed
	    (gimp-displays-flush)
	)

)

(script-fu-register 	"script-fu-ps-gradmap"
			"PS Gradient Map..."
			"Create Photoshop-style gradient map"
			"Devin Watson <>"
			"Devin Watson"
			"17 June 2008"
			"RGB*"
			SF-IMAGE 			_"Image"	  	  0
			SF-DRAWABLE 		_"Layer"		  0
			SF-COLOR 			_"Gradient Start" '(41 10 89)
			SF-COLOR 			_"Gradient End"   '(255 124 0)
			SF-ADJUSTMENT		_"Opacity"		  '(100 0 100 1 10 0 1)
			SF-TOGGLE    	 	_"Flatten Image"  FALSE
)

(script-fu-menu-register "script-fu-ps-gradmap"
			 "<Image>/Script-Fu/Artistic")
 -style-gradient-map-for-GIMP-5750-1.html  
 Seemed easy enough to convert into a plug-in, so I did
 The script is located in menu "<Image> / Script-Fu / Artistic / PS Gradient Map..."



 --------------------------------------------------------------------
  
 Changelog:
    - Initial plug-in script

 --------------------------------------------------------------------

 This program is free software; you can redistribute it and/or modify
 either version 3 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.
 
 along with this program; if not, you can view the GNU General Public
Save the original foreground and background colors
Select none
Add the duplicate layer to the image
Rename the layer
Desaturate the layer
Set the background color to gradEnd)
Run the gradient color map
Set the opacity level
Set the foreground and background colors back to their originals
Finish the undo group for the process
Ensure the updated image is displayed

  PS - style Gradient Map 
  by   
  Based on a tutorial found on the GimpTalk.com forums : 
  Last changed : 17 June 2008 
  Copyright ( C ) 2008   
   Version 0.1 
  it under the terms of the GNU General Public License as published by 
  You should have received a copy of the GNU General Public License 
  License version 3 at the web site -3.0.html 
  Alternatively you can write to the Free Software Foundation , Inc. , 675 Mass 
  Ave , Cambridge ,   , USA . 

(define (script-fu-ps-gradmap theImage theLayer gradStart gradEnd opacityLevel flattenImage?)

    (let* 
	    (
			(workLayer (car (gimp-layer-copy theLayer 0)))
			(orgFGColor (car (gimp-context-get-foreground)))
			(orgBGColor (car (gimp-context-get-background)))
	    )

Start an undo group so the process can be undone with one undo 
	    (gimp-image-undo-group-start theImage)

	    (gimp-selection-none theImage)

	    (gimp-image-add-layer theImage workLayer 0)

	    (gimp-drawable-set-name workLayer "Work Layer")

		(gimp-desaturate workLayer)

Set the foreground color to gradStart 
		(gimp-context-set-foreground gradStart)

		(gimp-context-set-background gradEnd)

		(plug-in-gradmap 1 theImage workLayer)

Set the layer mode to COLOR - MODE ( 13 ) 
		(gimp-layer-set-mode workLayer COLOR-MODE)

		(gimp-layer-set-opacity workLayer opacityLevel)

		(if (eqv? flattenImage? TRUE)
			(gimp-image-flatten theImage)
		)

		(gimp-context-set-background orgBGColor)
		(gimp-context-set-foreground orgFGColor)

	    (gimp-image-undo-group-end theImage)

	    (gimp-displays-flush)
	)

)

(script-fu-register 	"script-fu-ps-gradmap"
			"PS Gradient Map..."
			"Create Photoshop-style gradient map"
			"Devin Watson <>"
			"Devin Watson"
			"17 June 2008"
			"RGB*"
			SF-IMAGE 			_"Image"	  	  0
			SF-DRAWABLE 		_"Layer"		  0
			SF-COLOR 			_"Gradient Start" '(41 10 89)
			SF-COLOR 			_"Gradient End"   '(255 124 0)
			SF-ADJUSTMENT		_"Opacity"		  '(100 0 100 1 10 0 1)
			SF-TOGGLE    	 	_"Flatten Image"  FALSE
)

(script-fu-menu-register "script-fu-ps-gradmap"
			 "<Image>/Script-Fu/Artistic")