[plt-scheme] Image library bug?

From: Robby Findler (robby at eecs.northwestern.edu)
Date: Tue Dec 8 20:24:12 EST 2009

On Tue, Dec 8, 2009 at 5:40 PM, Jordan Johnson <jmj at fellowhuman.com> wrote:
> On Dec 7, 2009, at 4:37 PM, Robby Findler wrote:
>>> I see there isn't
>>> an equivalent of the image<->color-list functions in the new library; is
>>> that likely to make its way in eventually?  If not, it would be nice to
>>> have
>>> a way to make this work in the old version.
>> Yes, there will be something along these lines in 2htdp/image
>> eventually. But it won't be quite the same; specifically you'll only
>> be able to get back a bitmap not an image.
> This makes sense.
>>> If there are plans to support color structs in the 2e
>>> version, it'd be Really Neat if both kinds could work, or if alpha-colors
>>> were the only kind of color struct (perhaps with a constructor like
>>> make-color that creates a fully-opaque color).
>> I'd like to add something like slideshow's cellophane operator
>> instead, probably. Would that work okay for you?
> Yes, that seems reasonable.  I saw the "stamp" and "see-thru" operators in
> the source of private/image-more.ss -- are those the ones you're planning
> on?  That sounds good, if so...and incidentally, one of my students asked a
> question amounting to whether we can get the union, intersection, or
> difference of two images of shapes, and for his immediate purpose I think
> those two operators would have sufficed.

Union yes (well, overlay really); intersection no, since the shapes
representable by the internal shape datatype isn't closed under

Stamp is something I thought about, but probably won't end up doing. We'll see.


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