[plt-scheme] Re: Writing a game and have questions

On Sun, Sep 21, 2008 at 10:18 AM, Deep <deepankar.sharma at gmail.com> wrote:
> Thanks for the very detailed, prompt and helpful answers. I decided to
> ditch the offscreen-buffer based approach and instead decided to
> implement a convex polygon + point in poly approach.

Just in case you missed that earlier -- the GUI library in PLT Scheme
has support for that, so you don't need to dig out your old graphics
textbook.

Robby

> Neil - thanks for the suggestions, I found them really helpful.
> Mathew - thanks for the rendering tips, i have a feeling they will be
> useful in the future.
> Doug - It would be great if you could send me an example app.
>
> Thanks,
> Deepankar
>
>
>
> On Sep 21, 11:02 am, "Doug Williams" <m.douglas.willi... at gmail.com>
> wrote:
>> 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 <mfl... 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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>>
>>
>>  animated-canvas.ss
>> 4KViewDownload
>>
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