[plt-scheme] Writing a game and have questions

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.

Doug

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
>
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