Gimp script for whitening the background of all images in a folder. support jpg but can be adapted

whiten-background-gimp-script-fu.scm

(define (drop-ext str)
	(unbreakupstr (butlast (strbreakup  str ".")) ".")	
)
; extract basename without ext

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( define ( script-fu-whitenbackground 
   sourceDirectory targetDirectory )
   ( let*
      (
         ; Declare and Init local variables
         ( returnVal #f )
         ; Guess host OS based on directory path separator
         ( isLinux (  >  
            ( length ( strbreakup sourceDirectory "/" ) )
            ( length ( strbreakup sourceDirectory "\\" ) ) ) )
         ; Form path/file patternSource based on OS 
         ( patternSource ( if isLinux
            ( string-append sourceDirectory "/*.[jJ][pP][gG]" )
            ( string-append sourceDirectory "\\*.[jJ][pP][gG]" ) ) )
         ( patternTarget ( if isLinux
            ( string-append targetDirectory "/*.[jJ][pP][gG]" )
            ( string-append targetDirectory "\\*.[jJ][pP][gG]" ) ) )
         ; List of files to be converted formatted for current Host
         ; O/S
         ( filelistSource ( cadr ( file-glob patternSource 1 ) ) )
         ( filelistExists ( cadr ( file-glob patternTarget 1 ) ) )
         ( checkFileExists filelistExists )
         ; Place holders for image variables - updated per image
         ( theImage 0 )
				 ( theOrigLayer 0 )
				 ( theBgLayer 0 )
         ( theDrawable 0 )
         ( currentFile "" )
         ( baseName "" )
         ( outFilename "" )
         ; Constants used to assign values to parasites on new image
         ( doIt #t )
         ( checkFile "" )
				
				 
      ) ; End declaration of Local Variables
      ;
      ; Run if images closed, message if not.
      ( if ( < 0 ( car ( gimp-image-list ) ) )
         ( gimp-message "Close open Images & Rerun" )
         ( begin
            ;
            ; Run within scope of let* and local variables
            ; 'baseName' is filename without .jpg extension
            ; 'outFilename' is filename with .xcf extension
            ; Step through each file in list with while loop.
            ( while ( not ( null? filelistSource ) )
               ( set! doIt #t )
               ( set! checkFileExists filelistExists )
               ( set! currentFile ( car filelistSource ) )
               ; Get open and get Image ID of current file
               ( set! theImage
                  ( car ( gimp-file-load RUN-NONINTERACTIVE 
                     currentFile currentFile ) ) )
               ( if isLinux
                  ; Target path-filename if Host OS is Linux
                  ( begin 
                     ( set! baseName ( car ( reverse
                        ( strbreakup currentFile "/" ) ) ) )
                     ( set! baseName (drop-ext baseName ))
                     ( set! outFilename ( string-append
                           targetDirectory "/" baseName ".jpg" ) )
                  ) ; End begin - Host OS is Linux
                  ; Target path-filename if Host OS is Windows
                  ( begin 
                     ( set! baseName ( car ( reverse
                        ( strbreakup currentFile "\\" ) ) ) )
                     ( set! baseName (drop-ext baseName) )
                     ( set! outFilename ( string-append
                           targetDirectory "\\" baseName ".jpg" ) )
                  ) ; End begin - if Host OS is Windows
               ) ; End if isLinux
               ; Check to see if outFilename exists so we don't overwrite
               ( while ( not ( null? checkFileExists ) )
                  ( set! checkFile ( car checkFileExists ) )
                  ( if ( string=? outFilename checkFile )
                     ( set! doIt #f ) )
                  (set! checkFileExists ( cdr checkFileExists ) )
               ) ; End while checkFileExists
               ( if doIt
                  ( begin		    
                    ;; --------------------------------------
                    ;; add white bg layer
                    (set! theBgLayer (car (gimp-layer-new theImage (car (gimp-image-width theImage)) (car (gimp-image-height theImage)) 1 "bg" 100 0)))
                    (gimp-image-insert-layer theImage theBgLayer 0 1)
                    (gimp-edit-fill theBgLayer 1)
                    ;; change mode of original layer to HARDLIGHT-MODE (18)
                    (set! theOrigLayer (vector-ref (cadr (gimp-image-get-layers theImage)) 0))
                    (gimp-layer-set-mode theOrigLayer 18)
                    ; Get / set Drawable ID, need it for file save.
                    ( set! theDrawable ( car 
                    ( gimp-image-merge-visible-layers theImage 0 ) ) )
                    ; Save file 
                    ( gimp-file-save 
                      RUN-NONINTERACTIVE theImage theDrawable
                        outFilename outFilename )
                    ;; --------------------------------------
                  ) ; End begin
               ) ; End if doIt
							 
               ( gimp-image-delete theImage )
               ; Update while loop iteration parameter
               (set! filelistSource ( cdr filelistSource ) )
            ) ; End while
         ); End outer begin
      ) ; End outer if
      ( set! returnVal #t )
   ) ; End let*
) ; End define
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( script-fu-register "script-fu-whitenbackground" ; Function Name
   "1 ) Whiten JPG background (Directory)"    ; Menu Label
   "This script is an interactive script to whiten background of all of the jpegs 
   in a source directory to a target 
   directory.  The script is designed to be run WITHOUT ANY IMAGE 
   LOADED. Runs from GIMP shell in Linux and Windows."
   "Yawo KPOTUFE"       ; Author
   "2016, Yawo KPOTUFE" ; Copyright
   "November 2016"          ; Creation Date
   ""                   ; Valid Image Type - No Image required
    ; We actually don't want any images open when we run this
    ;   script, so it must be available from the menu when an
    ;   image is not loaded.  This script will determine the IDs
    ;   of the Image and Drawable itself rather than having them
    ;   passed as parameters.
   ; Interactive widgets
   SF-DIRNAME "JPG Originals (source) Directory" ""
   SF-DIRNAME "JOG Whitened   (target) Directory" ""
) ; End script-fu-register
( script-fu-menu-register 
   "script-fu-whitenbackground" "<Image>/WhitenBackground")
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