[plt-scheme] 2htdp/image

The new HtDP 2e image library is ready for earlier adopters. It isn't
part of the release that recently went out, but it is available in the
SVN build of DrScheme (and will be available tomorrow in the nightly
builds). At the moment, it contains only some basic image operations,
but I expect to be adding more over the coming weeks. Let me know if
there are particular operations that you'd like me to get to first.

Here's a quick list of the differences between this and the current
image teachpack:

  - copying and pasting does not introduce jaggies
  - equal comparisions are more efficient
  - added rotation & scaling
  - got rid of pinholes (see the new overlay, beside, etc functions)

All of the currently implemented functionality is documented here:

  http://pre.plt-scheme.org/docs/html/teachpack/2htdpimage.html

Thanks,
Robby