This is a script from Leon Koninin that removes paper backgrounds.
It can be a bit aggressive when the printing is light, but it's often a good first attempt.
(define (write_xc_message ws xc)
(let
((i 0))
(set! i 0)
(while (< i 3)
(set! ws
(string-append
ws
(number->string (aref xc i))
";"
)
)
(set! i (+ i 1))
)
(gimp-message ws)
)
)
(define (script-fu-back-to-white img)
(gimp-context-push)
(gimp-image-undo-group-start img)
(gimp-progress-set-text "Correcting background")
(let
(
(xc #(0 0 0))
(px #(0 0 0))
(dr 0)
(y 0)
(i 0)
)
(set! xc #(0 0 0))
(set! dr (car (gimp-image-get-active-drawable img)))
(set! i 0)
(while (< i 3)
(aset xc i 0)
(set! i (+ i 1))
)
;(write_xc_message "before: " xc)
(while (< y 100)
(set! i 0)
(set! px (cadr (gimp-drawable-get-pixel dr
(rand (- (car (gimp-drawable-width dr)) 1))
(rand (- (car (gimp-drawable-height dr)) 1))
))
)
(while (< i 3)
(aset xc i (+ (aref xc i) (aref px i) ) )
(set! i (+ i 1))
)
(set! y (+ y 1))
(gimp-progress-update (/ y 100))
)
;(write_xc_message "after: " xc)
(set! i 0)
(while (< i 3)
(set! y (round (/ (aref xc i) 100 ) ))
(gimp-levels dr (+ i 1) 0 y 1.0 0 255)
(set! i (+ i 1))
)
(gimp-levels dr 0 0 255 0.60 0 255)
(gimp-desaturate dr)
(gimp-layer-add-alpha dr)
(plug-in-colortoalpha 1 img dr '(255 255 255))
)
(gimp-image-undo-group-end img)
(gimp-displays-flush)
(gimp-progress-update 1.0)
(gimp-context-pop)
)
(define (batch-back-to-white pattern)
(let*
(
(filelist (cadr (file-glob (string-append pattern "\\*.jpg") 1)))
)
(while (not (null? filelist))
(let*
(
(filename (car filelist)
)
(image (car (gimp-file-load RUN-NONINTERACTIVE filename filename)))
(drawable (car (gimp-image-get-active-layer image))))
(script-fu-back-to-white image)
(gimp-file-save RUN-NONINTERACTIVE image drawable filename filename)
(gimp-image-delete image)
)
(set! filelist (cdr filelist))
)
)
)
(script-fu-register "script-fu-back-to-white"
"Reset background to white"
"Reset background, by changing channels levels upper value to average"
"Leonid Koninin"
"Leonid Koninin"
"2011"
"RGB*, GRAY*"
SF-IMAGE "Image" 0
)
(script-fu-register "batch-back-to-white"
"Reset background to white (all *.jpg in directory)"
"Reset background, by changing channels levels upper value to average"
"Leonid Koninin"
"Leonid Koninin"
"2011"
"RGB*, GRAY*"
SF-DIRNAME "Directory" ""
)
(script-fu-menu-register "script-fu-back-to-white"
"<Image>/Filters/Leon")
(script-fu-menu-register "batch-back-to-white"
"<Image>/Filters/Leon")