;; You should comment out the following line if you are NOT using
;; DrScheme.  In DrScheme, it reduces the sizes of images so stacked
;; images will (usually) fit in the DrScheme interaction window.

(set-default-image-size! 25)

;; Basic block for "Repeating Crosses" quilting pattern from
;; "Quick-and-Easy Strip Quilting" by Helen Whitson Rose, Dover
;; Publications, New York, 1989, p. 60.
(define rcross-bb
  (overlay (overlay (overlay (filled-triangle -1 1 1 1 -1/2 1/2)
                             (filled-triangle -1/2 1/2 1 1 1 1/2))
                    (overlay (filled-triangle 1 1/2 1/2 1/2 1/2 -1/2)
                             (filled-triangle 1/2 -1/2 1 -1 1 1/2)))
           (filled-triangle -1/2 1/2 -1/2 -1/2 1/2 -1/2)))

;; A much simpler basic block, with one corner black.
(define corner-bb
  (filled-triangle 0 1 1 1 1 0))

;; This one only has two trinagles, but makes an interesting pinwheel.
(define nova-bb
  (overlay (filled-triangle 0 1 0 0 -1/2 0)
           (filled-triangle 0 0 0 1/2 1 0)))

;; Basic block for "Blowing in the Wind" quilting pattern from
;; "Quick-and-Easy Strip Quilting" by Helen Whitson Rose, Dover
;; Publications, New York, 1989, p. 59.
(define bitw-bb
  (overlay (overlay (filled-triangle -1 1 0 1 -1/2 1/2)
                    (filled-triangle -1 -1 0 -1 -1 0))
           (overlay (filled-triangle 1 1 1 0 0 0)
                    (filled-triangle 0 0 1 0 1/2 -1/2))))

;; A simple test image, to illustrate transformations.
(define test-bb
  (filled-triangle 0 1 0 -1 1 -1))

(define black-bb
  (overlay (filled-triangle -1 -1 1 -1 1 1)
	   (filled-triangle -1 -1 -1 1 1 1)))

(define white-bb
  (invert black-bb))