Gimp-guide-center-box.scm

(define (guide-middle-box image drawable bwidth bheight)
	(let* (
				 (width (car (gimp-image-width image)))
				 (height (car (gimp-image-height image)))
				 (vmargin (/ (- width bwidth) 2))
				 (hmargin (/ (- height bheight) 2)))
		(if (and 
					(<= bwidth width) 
					(<= bheight height))
			(begin
				(gimp-image-add-vguide image vmargin)
				(gimp-image-add-vguide image (+ vmargin bwidth))
				(gimp-image-add-hguide image hmargin)
				(gimp-image-add-hguide image (+ hmargin bheight))
				(gimp-displays-flush))))
	)

(script-fu-register
	"guide-middle-box"
	"Guide Box"
	"Create guides on box edges, that positioned in middle of image.\
	User input width, and height(optional; else - height of image), then\
	the box fit in middle, and guides creates on it's edges."
	"Churin Dmitry"
	"As is"
	"October 26 2014"
	"*"
	SF-IMAGE 		"Image"		0 
	SF-DRAWABLE 		"Drawable" 	0
	SF-ADJUSTMENT		_"Bwidth"	(list 0 0 MAX-IMAGE-SIZE 1 10 0 1)
	SF-ADJUSTMENT		_"Bheight"	(list 0 0 MAX-IMAGE-SIZE 1 10 0 1)
	)

(script-fu-menu-register "guide-middle-box" "<Image>/Image/Guides")