<div dir="ltr">Here is a little demo - a not so good boids implementation.  But it shows how the animated canvas works.<br><br><div class="gmail_quote">On Sun, Sep 21, 2008 at 9:02 AM, Doug Williams <span dir="ltr"><<a href="mailto:m.douglas.williams@gmail.com">m.douglas.williams@gmail.com</a>></span> wrote:<br> <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div dir="ltr">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.<br> <font color="#888888"><br>Doug</font><div><div></div><div class="Wj3C7c"><br><br><div class="gmail_quote"> On Sun, Sep 21, 2008 at 7:58 AM, Matthew Flatt <span dir="ltr"><<a href="mailto:mflatt@cs.utah.edu" target="_blank">mflatt@cs.utah.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> Neil and Robby have given you good general answers --- compute the<br> target without referring to the image, or use regions instead of an<br> offscreen image --- but I'll answer the original questions:<br> <div><br> At Sat, 20 Sep 2008 11:23:32 -0400, "deepankar" wrote:<br> > 1) Is it possible to draw a canvas to an offscreen buffer ?<br> <br> </div>You can take a function that draws to a canvas and redirect it so that<br> it draws to an offscreen image (i.e., swap a `bitmap-dc%' in place of a<br> canvas `dc<%>').<br> <div><br> > 2) Is it possible to fetch pixel values from a canvas.<br> <br> </div>Canvas drawing is one-way only: you can send an image out to the user<br> to see, but you cannot programmatically "look" at the canvas. Also,<br> there's no way to take a snapshot of the canvas to get back an<br> offscreen image.<br> <br> If you redirect a drawing function to an offscreen image, then you<br> can, of course, inspect the pixels of the offscreen image.<br> <font color="#888888"><br> <br> Matthew<br> </font><div><div></div><div><br> _________________________________________________<br>  For list-related administrative tasks:<br>  <a href="http://list.cs.brown.edu/mailman/listinfo/plt-scheme" target="_blank">http://list.cs.brown.edu/mailman/listinfo/plt-scheme</a><br> </div></div></blockquote></div><br></div></div></div> </blockquote></div><br></div>