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Working with unsigned/signed types

 
 
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      12-20-2006
Hi everyone-
I've been away from coding for a while (I turned into a professional
photographer)...
So now I've taken up a project involving working with EXIF and XMP metadata in
image files (mainly JPEG and TIFF), and am having some trouble figuring out how
to handle some of the data...

Here's what I'm having to do:
Inside the files, there are various types of data which can be split apart and
organized fairly easily, given you have unsigned and signed types... Which is
where I'm running into problems remembering how everything works.

The first part of the question is fairly basic - in C, working with signed
integers, the MSB (is that still the right term?) is used to denote positive and
negative, and the following bits increase towards positive infinity, correct?
Such that in C, adding one to 0x7fffffff would cause the number to go around to
-0x7fffffff (or whatever that is), giving -1 for 0xffffffff?

Secondly, (and this is my weak point as a programmer) to re-insert the data
after, what would be the most efficient way to pull everything back apart into
individual characters for putting it all back into the files? I could probably
figure out something that would work, but I wouldn't be so sure as to its
reliability.

Third, being a photographer now rather than a coder, I'd like to give back the
modules I'm writing to the community (it looks like very little of the sort
exists), but would rather not worry about them in the future... Is there a good
way to go about this?

Thanks!
-Brian Shirk

Avalanche Photography LLC
www.AvalanchePhoto.com
McCall, Idaho
 
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