;;; File:
;;;   extra.scm
;;; Author:
;;;   Samuel A. Rebelsky
;;; Contents:
;;;   A variety of methods for exploration of "higher-order graphics"
;;;   with Script-Fu in the GIMP.
;;; Note:
;;;   These methods are generally and intentionally under-documented.

(define combine-images
  (lambda (layer0 layer1 combine)
    (let* ((x 0)
           (y 0)
           (width (car (gimp-drawable-width layer0)))
           (height (car (gimp-drawable-height layer1)))
           (newimg (new-image width height))
           (newlayer (cadr newimg)))
      (while (< y height)
        (set! x 0)
        ; (print (list "row" y))
        (while (< x width)
          (let* ((pixel0 (get-pixel layer0 x y))
                 (pixel1 (get-pixel layer1 x y ))
                 (newpixel (combine pixel0 pixel1)))
            ; (print (list x y pixel0 pixel1 newpixel)) ; DEBUG
            (set-pixel! newlayer x y newpixel)
            (set! x (+ x 1))))
        (set! y (+ y 1)))
      newimg)))

(define avg
  (lambda (ratio)
    (lambda (color0 color1)
      (rgb (+ (* ratio (red color0)) (* (- 1 ratio) (red color1)))
           (+ (* ratio (green color0)) (* (- 1 ratio) (green color1)))
           (+ (* ratio (blue color0)) (* (- 1 ratio) (blue color1)))))))

(define wrap
  (lambda (x)
    (cond
      ((> x 256) (- x 256))
      ((< x 0) (+ x 256))
      (#t x))))

(define silly
  (lambda (color0 color1)
    (rgb (wrap (+ (red color0) (red color1)))
         (wrap (+ (green color0) (green color1)))
         (wrap (+ (blue color0) (blue color1))))))

(define subtract
  (lambda (color0 color1)
    (rgb (wrap (- (red color0) (red color1)))
         (wrap (- (green color0) (green color1)))
         (wrap (- (blue color0) (blue color1))))))

; HACK!
(define copyTo
  (lambda (source sourcelayer target targetlayer n)
    (gimp-rect-select source 0 0 72 100 2 0 0)
    (gimp-edit-copy sourcelayer)
    (gimp-rect-select target (* n 72) 0 72 100 2 0 0)
    (gimp-edit-paste targetlayer TRUE)))