[plt-scheme] Writing a game and have questions

From: Doug Williams (m.douglas.williams at gmail.com)
Date: Sun Sep 21 11:02:42 EDT 2008

I have an animated canvas that I use for animation.  I've never put it up on
PLaneT, but use it for many of my own applications.  I can send an example
app if you want.


On Sun, Sep 21, 2008 at 7:58 AM, Matthew Flatt <mflatt at cs.utah.edu> wrote:

> Neil and Robby have given you good general answers --- compute the
> target without referring to the image, or use regions instead of an
> offscreen image --- but I'll answer the original questions:
> At Sat, 20 Sep 2008 11:23:32 -0400, "deepankar" wrote:
> > 1) Is it possible to draw a canvas to an offscreen buffer ?
> You can take a function that draws to a canvas and redirect it so that
> it draws to an offscreen image (i.e., swap a `bitmap-dc%' in place of a
> canvas `dc<%>').
> > 2) Is it possible to fetch pixel values from a canvas.
> Canvas drawing is one-way only: you can send an image out to the user
> to see, but you cannot programmatically "look" at the canvas. Also,
> there's no way to take a snapshot of the canvas to get back an
> offscreen image.
> If you redirect a drawing function to an offscreen image, then you
> can, of course, inspect the pixels of the offscreen image.
> Matthew
> _________________________________________________
>  For list-related administrative tasks:
>  http://list.cs.brown.edu/mailman/listinfo/plt-scheme
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.racket-lang.org/users/archive/attachments/20080921/d2b911f1/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: animated-canvas.ss
Type: application/octet-stream
Size: 3488 bytes
Desc: not available
URL: <http://lists.racket-lang.org/users/archive/attachments/20080921/d2b911f1/attachment.obj>

Posted on the users mailing list.