[plt-scheme] 2htdp/image

From: Robby Findler (robby at eecs.northwestern.edu)
Date: Mon Nov 16 21:12:21 EST 2009

On Mon, Nov 16, 2009 at 8:09 PM, Todd O'Bryan <toddobryan at gmail.com> wrote:
> 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?

All bitmaps are images.

> 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?

That requires someone better/smarter than me to figure out.


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