[plt-scheme] 2htdp/image

From: Todd O'Bryan (toddobryan at gmail.com)
Date: Mon Nov 16 21:09:45 EST 2009

On Mon, Nov 16, 2009 at 9:03 PM, Robby Findler
<robby at eecs.northwestern.edu> wrote:
> On Mon, Nov 16, 2009 at 7:58 PM, Nadeem Abdul Hamid <nadeem at acm.org> wrote:
>> 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.
So images from pasting or Insert Image... won't actually be images
anymore, but will be bitmaps?

In that case, do we need bitmap=? or something like that so we can
compare bitmaps to one another?

And will you be able to add-line to a bitmap or overlay images on top
of bitmaps, etc.?

This scares me a little. I understand the motivation, but I'm worried
that teaching the difference between images and bitmaps may be a
bigger pain than pinholes were. :-) Any way to hide the difference
from the user so that we get the speed-up where possible, but the
expected semantics where we can't do any better?


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