thank you so much! it works very well~! and I realize that the png files what I used is does not have any transparency could you let me know how to set a color as transparent as well?
On 21 November 2010 23:08, Matthew Flatt <mfl...@cs.utah.edu> wrote: > At Sun, 21 Nov 2010 10:55:22 +0900, 김태윤 wrote: > > it's about 10 hours since I stuck at overlaying several images > > (make only selected color to transparent) > > could somebody give me an little advice? > > just little hint about big picture would be very helpful for me. > > please~~! > > > > #lang racket/gui > > (define base-dc (make-object bitmap-dc% (make-object bitmap% 320 320 #f) > )) > > (define m-canvas% > > (class canvas% > > (override on-paint) > > (define on-paint (λ () (send (send this get-dc) draw-bitmap (send > > base-dc get-bitmap) 0 0))) > > (super-new))) > > (define color (make-object color% "red")) > > (define f (new frame% (label "a"))) > > (define c (new m-canvas% (parent f)(min-width 320) (min-height 320))) > > (send base-dc draw-bitmap (make-object bitmap% "./src/arena.png") 0 0 ) > > (send base-dc set-argb-pixels 0 0 288 256 (make-bytes (* 4 288 256))) > > (send base-dc draw-bitmap (make-object bitmap% "./src/char4.png") 0 0 ) > > (send f show #t) > > Is the problem that "arena.png" and "char4.png" are images with > transparency, but `draw-bitmap' draws them solid? > > If so, you need to supply 'png/mask as the after the pathname when > loading the bitmap > > (define bm1 (make-object bitmap% "./src/arena.png" 'png/mask)) > > and then use the bitmap mask when drawing: > > (send base-dc draw-bitmap bm1 > 0 0 solid > (send the-color-database find-color "black") > (send bm1 get-loaded-mask)) > > > It's much simpler in the current development version of Racket, where > transparency is more directly supported on bitmaps. In version > 5.0.99.2, > > (send base-dc draw-bitmap (read-bitmap "./src/arena.png") 0 0) > > automatically loads and uses transparency information. > >
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