[plt-dev] 2htdp/image: Where oh where have my pinholes gone?

From: Carl Eastlund (carl.eastlund at gmail.com)
Date: Wed Jan 13 12:01:15 EST 2010

On Wed, Jan 13, 2010 at 11:56 AM, Robby Findler
<robby at eecs.northwestern.edu> wrote:
> On Wed, Jan 13, 2010 at 10:42 AM, Carl Eastlund <carl.eastlund at gmail.com> wrote:
>> I wouldn't want the default pinhole drawing to pass through the image.
>>  That makes it harder to see if the contents of the image are the
>> same, for any pixels that fall under that black line.
> Drawing with 50% opacity is going to make it pretty easy to see the
> difference, I think. You'll be able to see "underneath" the lines. And
> I believe that this has the property that comparing the images,
> exactly as drawn, should be the same as comparing the images without
> the extra lines and then comparing the pinhole coordinates (well, not
> quite since the colors only use 2^24 different values, ie a fixed,
> small set of integers instead of rationals, but in practice it will
> work well I expect).
> But we'll want to experiment with this to see how it looks.
>> Single pixels
>> can matter.  I'd rather have something just at the edges.  I recognize
>> that for a large image, that can become hard to interpolate the
>> pinhole point, which is why I suggested the numeric display.
>> Maybe we can make the display more interactive, like syntax snips are.
>>  Give right-click options for show pinhole / hide pinhole / numeric
>> pinhole, etc.
> This is also a good idea, but I think we want to have something that
> looks good and is informative that doesn't make the image any bigger
> (as a default) and then go from there.

We're on the same wavelength; at this point, I'll wait to see how the
experiment turns out.  :)


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