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attempt to clarify the overlay/xy and underlay/xy documentation

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Merge to 5.1
This commit is contained in:
Robby Findler 2011-01-31 06:43:47 -06:00
parent fad47541b2
commit 3add4bce4d
1 changed files with 15 additions and 10 deletions
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25
collects/teachpack/2htdp/scribblings/image.scrbl
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@ -661,17 +661,21 @@ the @scheme[point-count] argument determines how many points the star has.
}
@defproc[(overlay/xy [i1 image?] [x real?] [y real?] [i2 image?]) image?]{
Constructs an image by overlaying @racket[i1] on top of @racket[i2] after
shifting @racket[i2] over by @racket[x] pixels to the right and @racket[y]
pixels down.
Constructs an image by overlaying @racket[i1] on top of @racket[i2].
The images are initially lined up on their upper-left corners and
then @racket[i2] is shifted to the right
by @racket[x] pixels to and down by @racket[y] pixels.
This is the same as @racket[(underlay/xy i2 (- x) (- y) i1)].
@image-examples[(overlay/xy (rectangle 20 20 "outline" "black")
20 0
(rectangle 20 20 "outline" "black"))
(overlay/xy (rectangle 20 20 "solid" "red")
20 20
10 10
(rectangle 20 20 "solid" "black"))
(overlay/xy (rectangle 20 20 "solid" "red")
-20 -20
-10 -10
(rectangle 20 20 "solid" "black"))
(overlay/xy
(overlay/xy (ellipse 40 40 "outline" "black")
@ -738,9 +742,10 @@ the @scheme[point-count] argument determines how many points the star has.
}
@defproc[(underlay/xy [i1 image?] [x real?] [y real?] [i2 image?]) image?]{
Constructs an image by underlaying @racket[i1] underneath of @racket[i2] after
shifting @racket[i2] over by @racket[x] pixels to the right and @racket[y]
pixels down.
Constructs an image by underlaying @racket[i1] underneath @racket[i2].
The images are initially lined up on their upper-left corners and
then @racket[i2] is shifted to the right
by @racket[x] pixels to and down by @racket[y] pixels.
This is the same as @racket[(overlay/xy i2 (- x) (- y) i1)].
@ -748,10 +753,10 @@ the @scheme[point-count] argument determines how many points the star has.
20 0
(rectangle 20 20 "outline" "black"))
(underlay/xy (rectangle 20 20 "solid" "red")
20 20
10 10
(rectangle 20 20 "solid" "black"))
(underlay/xy (rectangle 20 20 "solid" "red")
-20 -20
-10 -10
(rectangle 20 20 "solid" "black"))
(underlay/xy
(underlay/xy (ellipse 40 40 "solid" "gray")