Oh, I see. In that case, they should use the render-image function directly. Override the on-paint method, call the get-dc method and pass that and some suitable coordinates to do the drawing. I recommend using this only for drawing the final image, don't use other dc methods (I mean, you can, but you don't want to).
But a much better approach overall is to use the universe library: http://docs.racket-lang.org/teachpack/2htdpuniverse.html Robby On Thu, Mar 19, 2015 at 9:53 PM, Andrew Mauer-Oats <mauero...@gmail.com> wrote: > Thanks. Yes, they want to (say) draw a solid green circle next to the name > of someone who has been active in the last five minutes. As I understand it, > they followed the GUI Toolkit intro and arrived at the point where they have > a canvas% with the on-paint method specified in its constructor. The > on-paint method then needs to draw the green circle. They are familiar with > (circle 20 "solid" "green"), so they just want to do the equivalent of > (place-image green-circle x y ?dc?). > > I think the image->bitmap function Alexander provided looks like what they > need, and then they can use the draw-bitmap message. > > I didn't know how to pull the functions from different packages to make them > usable one file. > > Thanks for the help. > > Andrew > > > Andrew Mauer-Oats > Mathematics Ph.D. > Chicago Public Schools: Whitney Young > > On Thu, Mar 19, 2015 at 8:15 PM, Alexander D. Knauth <alexan...@knauth.org> > wrote: >> >> Here’s one way, if you mean a bitmap% object: >> >> #lang racket/base >> >> (provide image->bitmap) >> >> (require racket/class >> (only-in racket/draw make-bitmap bitmap-dc%) >> (only-in 2htdp/image image-width image-height) >> (only-in mrlib/image-core render-image)) >> >> (define (image->bitmap image) >> (let* ([width (image-width image)] >> [height (image-height image)] >> [bm (make-bitmap width height)] >> [dc (make-object bitmap-dc% bm)]) >> (send dc clear) >> (render-image image dc 0 0) >> bm)) >> >> >> On Mar 19, 2015, at 7:05 PM, Robby Findler <ro...@eecs.northwestern.edu> >> wrote: >> >> > When you say "bitmap" do you mean "bitmap% object"? And if so, why do >> > they want to do that? If not, do you mean something else? >> > >> > Robby >> > >> > >> > On Thu, Mar 19, 2015 at 5:24 PM, Andrew Mauer-Oats <mauero...@gmail.com> >> > wrote: >> >> Is there a public way to change an image created using the 2htdp/image >> >> library into a bitmap? >> >> >> >> My students are used to those functions and it would be easier for some >> >> of >> >> them to go and build the GUI they want if they didn't have to change >> >> over to >> >> explicitly using drawing contexts. >> >> >> >> I have looked at the source for mrlib/image-core, >> >> 2htdp/private/image-more, >> >> and 2htdp/image. It looks like no exported functions can change an >> >> image to >> >> a bitmap. >> >> >> >> The only thing they want to do is be able to render an image onto a dc. >> >> Presumably the render-image function would do that, were it exported. >> >> >> >> What should I do? >> >> >> >> Thanks for your help, >> >> >> >> Andrew Mauer-Oats >> >> Mathematics Ph.D. >> >> Chicago Public Schools: Whitney Young >> >> >> >> ____________________ >> >> Racket Users list: >> >> http://lists.racket-lang.org/users >> >> >> > ____________________ >> > Racket Users list: >> > http://lists.racket-lang.org/users >> > > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users > ____________________ Racket Users list: http://lists.racket-lang.org/users
