By the way, the same sort of bug affects draw-ellipse and canvas%. -- Garrett Mitchener
On Thu, May 10, 2012 at 11:10 AM, Garrett Mitchener < garrett.mitche...@gmail.com> wrote: > Okay, yes, using a dc-path% seems to work as intended. > > Thanks! > > -- Garrett Mitchener > > On Thu, May 10, 2012 at 11:04 AM, Matthew Flatt <mfl...@cs.utah.edu>wrote: > >> Although pixel alignment can be confusing, I think this one is just a >> bug. >> >> The `draw-rectangle' method tries to adjust the width of an outline so >> that in the simple case --- a width 0 or 1 pen in unsmoothed or aligned >> mode with a bitmap target --- the rectangle outline is the given width >> and height, instead of extending an extra pixel. That adjustment isn't >> implemented correctly, and the problem is particularly clear with a >> large scaling factor. >> >> You can work around the problem by creating a rectangle `dc-path%' and >> drawing it with `draw-path'. Meanwhile, I'll fix `draw-rectangle'. >> >> At Thu, 10 May 2012 09:57:26 -0500, Robby Findler wrote: >> > The problem is that the coordinates are "between" the pixels. There is >> an >> > explanation of this in the context of another library, but the issues >> are >> > the same: >> > >> > >> > >> http://docs.racket-lang.org/teachpack/2htdpimage.html?q=2htdp/image#%28part._nitty-g >> > ritty%29 >> > >> > hth, >> > Robby >> > >> > On Thu, May 10, 2012 at 8:29 AM, Garrett Mitchener < >> > garrett.mitche...@gmail.com> wrote: >> > >> > > Hi, I'm learning the racket GUI package, and I ran into something that >> > > doesn't make sense to me: >> > > >> > > #lang racket/gui >> > > >> > > (define black-pen >> > > (new pen% >> > > [width 1] >> > > [color "black"])) >> > > >> > > (define blue-brush >> > > (new brush% >> > > [color "blue"])) >> > > >> > > (define (draw-test-2 dc) >> > > (send dc scale 10 10) >> > > (send dc set-pen black-pen) >> > > (send dc set-brush blue-brush) >> > > (send dc draw-rectangle 7 2 4 4)) >> > > >> > > (define pic (make-bitmap 200 100)) >> > > >> > > (define dc (new bitmap-dc% [bitmap pic])) >> > > >> > > (draw-test-2 dc) >> > > >> > > And at the end, pic looks like this: >> > > >> > > [image: Inline image 1] >> > > The outline and the filling don't line up. What am I doing wrong? >> This >> > > is with DrRacket 5.2.1 on linux. >> > > >> > > Thanks, >> > > -- Garrett Mitchener >> > > >> > > ____________________ >> > > Racket Users list: >> > > http://lists.racket-lang.org/users >> > > >> > > >> > ____________________ >> > Racket Users list: >> > http://lists.racket-lang.org/users >> > >
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