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Crop rotated photos

A script-fu for The Gimp

Example

Image after running the script-fu 'Crop rotated photos'

Description

"Crop rotated photos" is a script-fu for the Gimp. To correct photos showing slightly slanted horizon lines or slanted vertical axes, you need to rotate the image by a small angle with an image editor. After such a rotation you get an image with slanted edges. Some image editors will eventually crop these slanted edges away automatically while others don't.

The Script-Fu "Crop rotated photos" for the Gimp is a function that crops automatically the slanted edges of rotated pictures and keeps the original aspect ratio.

On the example above we did not check the check box of the script, so that the result is not yet cropped but shows through a seleted area where the script would crop. However, if you check the checkbox of the script, the image will be cropped after execution of the script.

It has been tested with The Gimp version 2.2.9 on Linux SuSE and with The Gimp version 2.2.3 on Windoze.

The script version 1.10 has been tested with The Gimp version 2.4.0 on Linux Ubuntu 7.10 Gutsy Gibbon.

Versions

2007.10.26 : The current version is 1.10 and has been adapted to The Gimp 2.4.

Download:

Click into the blue frame below where the script is listed.
Type Control-A to select the complete text of the script.
Type Control-C to copy the script to the clipboard.
Go to your text editor (gedit, Kate, Aedix, Notepad, etc) and type Control-V to paste the script.
Save it as a file named crop-rotated-photo.scm

Linux Ubuntu or other Gnome:   use the text editor gedit or bluefish

Linux Kubuntu or other KDE:   use the text editor Kate or Quanta

Mac OS X:   use the text editor Smultron

Windoze:   use the text editor Aedix (free), or Notepad (but beware of the file extension .txt which is unwanted, the script file must have the extension .scm and not .scm.txt)

Other text editors are ok too, but word processors are not. Do not use Word, OpenOffice or similar tools.

Installation:

Copy crop-rotated-photo.scm into one of the directories registered in the Gimp preferences under Folders/Scripts.

Linux Ubuntu and many others:
  /home/[username]/.gimp-2.n/scripts   or   /usr/share/gimp/2.0/scripts

Linux SuSE:
  /home/[username]/.gimp-2.n/scripts   or   /opt/gnome/share/gimp/2.0/scripts

Windoze:
  C:\.gimp-2.n\scripts   or   C:\program-files\gimp2.n\share\gimp\scripts

Then go to the menu Xtns and select Xtns/Script-Fu/Refresh Scripts. That's it. You need to rotate your image by a small angle before calling the script "Crop Rotated Photo".

Successor:

The newer script correct-horizon does both things, it rotates and crops the photo.

Script-fu crop-rotated-photo.scm for The Gimp

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;
; SCRIPT-FU-CROP-ROTATED-PHOTO crops the slanted edges of an image obtained after a rotation by a small angle
; Copyright (c) 2006 Tharsice Demand <www.td-e.com>
; version 1.00  2006.07.06
; version 1.10  2007.10.26, migration to Gimp 2.4
;
;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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
;
;Copy of the license at http://td-e.com/site/gpl.php

(define (script-fu-crop-rotated-photo image drawable crop)

(gimp-image-undo-group-start image)

; alpha to selection will select the transparent slanted parts obtained after rotation
  (gimp-selection-layer-alpha drawable)

; defining the rectangle inscribed in the slanted rectangle obtained after rotation
  (let* 
    ((image-wi     (car (gimp-image-width image)))
     (image-he     (car (gimp-image-height image)))
     (image-r      (/ image-wi image-he))
     (lolimit-wi   (/ image-wi 2))
     (ii           0)
     (rect-x0      0)
     (rect-y0      0)
     (rect-x1      image-wi)
     (rect-y1      image-he)
     (rect-wi      image-wi)
     (rect-he      image-he)
     (corner00     0)
     (corner01     0)
     (corner10     0)
     (corner11     0)
     (msgwa        "")
     (cornersvalid 0)
     (posfound     0)
     (msg1         "")
     (msg2         "")
     (msga         "")
     (msgb         "")
     (msge         "")
     (msgz         "")
    )

; searching the inscribed rectangle through a while loop
    (while (< posfound 1)
      ; decrementing the size of the testing rectangle
      (set! rect-wi      (- rect-wi 2))
      (set! rect-he      (/ rect-wi image-r))
      (set! rect-x0      (/ (- image-wi rect-wi) 2))
      (set! rect-y0      (/ (- image-he rect-he) 2))
      (set! rect-x1      (+ rect-x0 rect-wi))
      (set! rect-y1      (+ rect-y0 rect-he))

; getting the selection values of the 4 corners of the testing rectangle, selected=transparent, or not
      (set! corner00 (car (gimp-selection-value image rect-x0 rect-y0)))
      (set! corner01 (car (gimp-selection-value image rect-x0 rect-y1)))
      (set! corner10 (car (gimp-selection-value image rect-x1 rect-y0)))
      (set! corner11 (car (gimp-selection-value image rect-x1 rect-y1)))

; if all 4 corners are valid=not transparent, the rectangle is inscribed in the slanted rectangle
      (if (> corner00 0) 
        (if (> corner01 0) 
          (if (> corner10 0) 
            (if (> corner11 0) 
              (set! cornersvalid 1)
            )
          )
        )
      )

; preparing the exit of the loop
      (if (= cornersvalid 1) (set! posfound 1))
      (if (< rect-wi lolimit-wi) (set! posfound 1))
      (set! ii (+ ii 1))
      (if (> ii 3000) (set! posfound 1))
    ) ; end of loop

; preparing error messages
    (if (< rect-wi lolimit-wi) (set! msg1 "Cropping area could not be defined, width/2 reached\n")
                               (set! msg1 ""))
    (if (> ii 3000) (set! msg2 "Cropping area could not be defined after 3000 loops\n")
                    (set! msg2 ""))
    (set! msge (string-append msg1 msg2))

; preparing debug messages
    (set! msga (string-append "Searched for " (number->string ii) " loops"
      "\n cornersvalid=" (number->string cornersvalid)
      "\n posfound=" (number->string posfound)
    ))
    (set! msgb (string-append "Selection values:"
      "\n x0=" (number->string rect-x0)
      "\n y0=" (number->string rect-y0)
      "\n x1=" (number->string rect-x1)
      "\n y1=" (number->string rect-y1)
      "\n corner00=" (number->string corner00)
      "\n corner10=" (number->string corner10)
      "\n corner01=" (number->string corner01)
      "\n corner11=" (number->string corner11)
     ))

; deciding whether to show error messages
    (if (> (string-length msge) 0)
      (begin
        (set! msgz (string-append msge "\n" msgb))
        (gimp-message msgz))
      ; else branch for debugging, to be commented in working version
      ;(begin
      ;  ;(set! msgz (string-append msge "\n" msgwa "\n\n" msga "\n\n" msgb))
      ;  (set! msgz (string-append msge "\n\n" msga "\n\n" msgb))
      ;  (gimp-message msgz)
    )

(if (eq? crop TRUE)
        (begin
          (gimp-crop image rect-wi rect-he rect-x0 rect-y0)
          (gimp-selection-clear image))
        (gimp-rect-select image rect-x0 rect-y0 rect-wi rect-he 2 0 0))
    (gimp-displays-flush)
  )
  (gimp-image-undo-group-end image)
)

(script-fu-register "script-fu-crop-rotated-photo"
                    "<Image>/Layer/Transform/Crop Rotated Photo..."
                    "Eliminates the slanted edges after a small rotation. Small rotations are often used to correct slightly slanted horizon lines or slightly slanted vertical axes on photos. Crops to a rectangle inscribed in the slanted rectangle obtained after rotations if the crop check-box is cheked, otherwise only selects the area it would crop to. Keeps the original aspect ratio."
                    "Tharsice Demand <td-e.com>"
                    "Tharsice Demand"
                    "2007.10.26"
                    "RGBA"
                    SF-IMAGE    "Image" 0
                    SF-DRAWABLE "Drawable" 0
                    SF-TOGGLE   "Crop Image\n(else select area to crop only)" TRUE
)

Sponsorship

If you find the script 'Crop rotated photos' useful and want to support the developer, you can

License

The GNU general public license applies to the script-fu crop-rotated-photo.scm above.

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