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fix problem with rotation on images such as bitmaps

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and replace internal `bring-between' with an efficient version
 Closes PR 11124
This commit is contained in:
Matthew Flatt 2010-08-30 19:18:08 -06:00
parent 7e1a6ec908
commit e0d9d2565c
2 changed files with 22 additions and 14 deletions
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21
collects/2htdp/private/image-more.rkt
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@ -616,8 +616,8 @@
(make-bitmap (bitmap-raw-bitmap bitmap)
(bitmap-raw-mask bitmap)
(bring-between (if flipped?
(+ θ (bitmap-angle bitmap))
(- (+ θ (bitmap-angle bitmap))))
(- (bitmap-angle bitmap) θ)
(+ (bitmap-angle bitmap) θ))
360)
(bitmap-x-scale bitmap)
(bitmap-y-scale bitmap)
@ -647,19 +647,14 @@
(make-point x y)))
;; bring-between : number number -> number
;; returns a number that is much like the modulo of 'x' and 'upper-bound'
;; but does this by repeated subtraction (or addition if it is negative),
;; bring-between : rational integer -> rational
;; returns a number that is much like the modulo of 'x' and 'upper-bound',
;; since modulo only works on integers
(define (bring-between x upper-bound)
(let loop ([x x])
(cond
[(< x 0)
(loop (+ x upper-bound))]
[(< x upper-bound)
x]
[else
(loop (- x upper-bound))])))
(let* ([x-floor (floor x)]
[fraction (- x x-floor)])
(+ (modulo x-floor upper-bound)
fraction)))
(define/chk (flip-horizontal image)
(rotate 90 (flip-vertical (rotate -90 image))))

15
collects/2htdp/tests/test-image.rkt
View File

@ -1262,15 +1262,28 @@
=>
(image-snip->image (make-object image-snip% blue-20x10-bitmap)))
(test (rotate 90 (make-object image-snip% green-blue-20x10-bitmap))
(test (rotate -90 (make-object image-snip% green-blue-20x10-bitmap))
=>
(image-snip->image (make-object image-snip% green-blue-10x20-bitmap)))
(test (rotate 90 (rotate 90 (make-object image-snip% green-blue-20x10-bitmap)))
=>
(rotate 180 (make-object image-snip% green-blue-20x10-bitmap)))
(test (rotate 90 (flip-vertical (rotate 90 (make-object image-snip% green-blue-20x10-bitmap))))
=>
(rotate 0 (make-object image-snip% green-blue-20x10-bitmap)))
;; there was a bug in the bounding box computation for scaled bitmaps that this test exposes
(test (image-width (frame (rotate 90 (scale 1/2 (bitmap icons/plt-logo-red-diffuse.png)))))
=>
128)
;; Rotation by 0 should produce an equivalent object
(test (rotate 0 (make-object image-snip% green-blue-20x10-bitmap))
=>
(to-img (make-object image-snip% green-blue-20x10-bitmap)))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; cropping (and place-image)