[plt-scheme] help : White color and "get-pixel" on Viewport graphics.

Hi,

thank you for your reply,

yes I tryied to set the pixel with the 
(make-rgb 1 1 1) but unfortunatly the result is the
same.

My platform is a SuSE Linux 7.0 , I'm using PLT Scheme
203.

Are the RGB values on your system different?

Alex

--- Robby Findler <robby at cs.uchicago.edu> wrote:
>   For list-related administrative tasks:
>  
> http://list.cs.brown.edu/mailman/listinfo/plt-scheme
> 
> What platofmr are you using? It works correctly for
> me on macos x.
> 
> One thing to try is replacing "white" with:
> 
>   (make-rgb 1 1 1)
> 
> Does that help?
> 
> Robby
> 
> At Sat, 12 Apr 2003 12:35:44 -0700 (PDT),
> "A.Pasquino" wrote:
> >   For list-related administrative tasks:
> >  
> http://list.cs.brown.edu/mailman/listinfo/plt-scheme
> > 
> > Hi all ,
> > 
> > (this is my first post) 
> > 
> > I'm doing some little tests with the Viewport
> library,
> > 
> > I have a little problem at using the "get-pixel"
> > operation.
> > 
> > In particular when I call this function on a white
> > pixel the result is '1' (but according to the
> manual
> > it should be '0'). 
> > 
> > I noticed that when I draw a white pixel the
> values of
> > the RGB colors are R=248/255 G=84/85 B=248/255,
> maybe
> > the "get-pixel" actually tests for a 255/255 R/G/B
> > value and so it replies 1?
> > (you can get the same values from an empty window
> > without drawing a white pixel with the
> "draw-pixel"). 
> > 
> > How can I set a 'true' white in order to get
> > a 0 from the 'get-pixel' function? 
> > Maybe I misunderstood how to use these functions? 
> > Any help is welcome, Thank you in advance.
> > 
> > Alex. 
> > 
> > PS: thank you to the PLT team for your Great
> > Environment! 
> > 
> > This is my test code: 
> > 
> > it should open a 10x10 pixels window and draw a
> white
> > pixel in the center, position (4,4)
> > (actually the "draw-pixel" is not necessary). 
> > 
> > (require (lib "graphics.ss" "graphics")) 
> > (define (test)
> >   (open-graphics)   
> > 
> >   (let ((my-port (open-viewport "rgb-test" 10 10))
> >         (position (make-posn 4 4)))
> >     ((draw-pixel my-port) position "white")
> >     (display ((get-pixel my-port) position))
> > 
> >     (let ((pix-color ((get-color-pixel my-port)
> > position)))
> >       (newline)
> >       (display (rgb-red pix-color))(display " ")
> >       (display (rgb-green pix-color))(display " ")
> >       (display (rgb-blue pix-color))(display " "))
> >     (close-viewport my-port)
> >     )
> >   (close-graphics)
> >   )
> >    
> > >(test)
> > 1
> > 248/255 84/85 248/255
> > 
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