[racket] draw circle over bitmap and erase old circle

omg it works!!
thank you!
although I am satisfied with this method,
do you know the better way for it?

, Richard Cleis <rcleis at mac.com>님이 작성:
> Insert the two lines below to see that what you want is possible, but I  
> doubt such a quick hack is the right way to do it.



> rac



> On Oct 27, 2010, at 8:48 PM, kty1104 at gmail.com wrote:



> > hello

> > I finally circle the bitmap where I point by mouse

> > but there are several problem

> > 1. the circle filled with white color that I can't see bitmap through  
> the circle

> > 2. the drawn circle didn't erased after I point another coordinates

> >

> > could somebody give me an little advice?

> >

> > my code looks messy and not neat but

> > I paste the code for make it easier to understand

> >

> >

> > #lang scheme

> > (require 2htdp/image

> > racket/gui)

> > (define chipset (make-object bitmap% "town.png" 'png))

> > (define (check dc m)





> (send dc draw-bitmap chipset 0 0)

> (send dc set-brush "blue" 'transparent)







> > (define x (send m get-x))

> > (define y (send m get-y))

> > (send dc draw-ellipse (- x (modulo x 16)) (- y (modulo y 16)) 16 16))

> > (define f (new frame% (label "map editor")))

> > (define xymsg (new message% (label "nth so far") (parent f)))

> > (define select%

> > (class canvas%

> > (override on-event on-paint)

> > (define on-paint (λ () (send (send this get-dc) draw-bitmap chipset 0  
> 0)))

> > (define on-event (λ (m)

> > (send xymsg set-label

> > (string-append "x:"

> > (number->string (send m get-x))

> > " y:"

> > (number->string (send m get-y))))

> > (when (send m get-left-down) (check (send this get-dc) m))))

> >

> > (super-new )

> > ))

> > (new select% (parent f) (min-width (image-width chipset)) (min-height  
> (image-height chipset)) )

> > (send f show #t)_________________________________________________

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> > http://lists.racket-lang.org/listinfo/users




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