[plt-scheme] 2htdp/image

From: Robby Findler (robby at eecs.northwestern.edu)
Date: Mon Nov 16 21:03:22 EST 2009

On Mon, Nov 16, 2009 at 7:58 PM, Nadeem Abdul Hamid <nadeem at acm.org> wrote:
> On Nov 16, 2009, at 8:47 PM, Robby Findler wrote:
> It isn't possible to write color-list->image anymore, but I was
> planning to add color-list->bitmap and image->color-list eventually,
> yes.
> image->color-list and color-list->image are really useful for exercises like
> "negative-image" that get students to apply some function to a list of color
> structures and then see the effect. (It's the kind of thing the "media
> computation" folks get excited about.)
> What's the connection between bitmap and image?

In the old library, images were bitmaps (essentially, with some
optimizations). This led to some performance problems, esp. on older
machines, so in the new library, images are roughly trees of overlaid
images with polygons, ellipses, text, and bitmaps at the leaves.

So, if I have a collection of colors, I can make a bitmap but not
figure out what the tree would have been. You'll be able to see the
difference if you rotate or (especially) scale the image. If it is a
tree of overlaid polygons, say, then scaling will work perfectly, but
the bitmap scaling won't look as good.


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