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, kty1...@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)_________________________________________________ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/users _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
