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applied Ian's patch to the bitmap rotation code

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svn: r17513

original commit: b5e54fe2eb642c41bf70ceeaabe37eb34d84ac2a
This commit is contained in:
Robby Findler 2010-01-06 21:43:34 +00:00
parent f4c8b595d4
commit 2c7ebeae74
2 changed files with 27 additions and 20 deletions
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19
collects/mrlib/image-core.ss
View File

@ -90,9 +90,6 @@ has been moved out).
(define (image-normalized? p) (send p get-normalized?))
(define (set-image-shape! p s) (send p set-shape s))
(define (set-image-normalized?! p n?) (send p set-normalized? n?))
(define (image-right image) (bb-right (image-bb image)))
(define (image-bottom image) (bb-bottom (image-bb image)))
(define (image-baseline image) (bb-baseline (image-bb image)))
(define (image? p)
(or (is-a? p image%)
(is-a? p image-snip%)
@ -242,11 +239,10 @@ has been moved out).
(init-field shape bb normalized?)
(define/public (equal-to? that eq-recur)
(or (eq? this that)
(and (eq-recur bb (send that get-bb))
(let* ([w (ceiling (max (inexact->exact (bb-right bb))
(inexact->exact (bb-right (send that get-bb)))))]
[h (ceiling (max (inexact->exact (bb-bottom bb))
(inexact->exact (bb-bottom (send that get-bb)))))]
(and (is-a? that image%)
(same-bb? bb (send that get-bb))
(let* ([w (round (inexact->exact (bb-right bb)))]
[h (round (inexact->exact (bb-bottom bb)))]
[bm1 (make-object bitmap% w h)]
[bm2 (make-object bitmap% w h)]
[bytes1 (make-bytes (* w h 4) 0)]
@ -341,6 +337,10 @@ has been moved out).
(inherit set-snipclass)
(set-snipclass snip-class)))
(define (same-bb? bb1 bb2)
(and (= (round (bb-right bb1)) (round (bb-right bb2)))
(= (round (bb-bottom bb1)) (round (bb-bottom bb2)))
(= (round (bb-baseline bb1)) (round (bb-baseline bb2)))))
(define scheme/base:read read)
(define image-snipclass%
@ -808,9 +808,6 @@ the mask bitmap and the original bitmap are all together in a single bytes!
ellipse-rotated-size
image?
image-right
image-bottom
image-baseline
text->font
compare-all-rotations

20
collects/mrlib/private/image-core-bitmap.ss
View File

@ -97,7 +97,7 @@ instead of this scaling code, we use the dc<%>'s scaling code.
(values (build-bmbytes new-w
new-h
(λ (x y)
(let* {[pre-image (* (make-rectangular (+ west x) (- nrth y))
(let* {[pre-image (* (make-rectangular (+ west x 1/2) (- nrth y 1/2))
theta-unrotation)]
}
(interpolate bmbytes w h
@ -105,6 +105,16 @@ instead of this scaling code, we use the dc<%>'s scaling code.
(- (imag-part pre-image))))))
new-w
new-h)))
;; Why the offsets of 1/2 in `rotate-bytes` and `interpolate`?
;; We consider a pixel's RGB as a point-sample taken from the 'true' image,
;; where the RGB is the sample at the *center* of the square covered by the pixel.
;; (When we assume the sample had been from the NW corner instead of the center,
;; we got weird artifacts upon rotation:
;; Consider a 1x1 bitmap rotated by 90 degrees.
;; The NW corner of our new value would be derived from the *NE* corner of
;; the original bitmap, which is a full pixel-width away from the original sample.
;; So a 1x1 bitmap being rotated would counterintuitively give a different bitmap.)
; interpolate: bytes natnum natum real real -> bytes
@ -114,10 +124,10 @@ instead of this scaling code, we use the dc<%>'s scaling code.
; where x,y are *real-valued* coordinates in [0,w), [0,h).
;
(define (interpolate bmbytes w h x y)
(let* {[x0 (floor/e x)]
[y0 (floor/e y)]
[dx (- x x0)]
[dy (- y y0)]
(let* {[x0 (floor/e (- x 1/2))]
[y0 (floor/e (- y 1/2))]
[dx (- (- x 1/2) x0)]
[dy (- (- y 1/2) y0)]
[1-dx (- 1 dx)]
[1-dy (- 1 dy)]
[nw (bmbytes-ref/safe bmbytes w h x0 y0 )]