Invisible wrote:

> I'm currently writing a small Haskell library for this. Currently it 
> understands 2 of 5 standard and interleaved, code 128, and I'm currently 
> implementing code 39. Of course, the library only handles converting 
> characters into 1s and 0s and back again. In "real" barcode handling 
> things are far more complex; bar thicknesses have to be within certain 
> tollerances when printing, and scanning is a fairly sophisticated 
> problem...

I added a function which spits out a PostScript file containing the 
barcode. Printed one out and compared it to a real barcode that encodes 
the same messages. It seems the bar thicknesses don't quite match, but 
otherwise it's quite similar.

In particular, Code 39 uses thin and thick bars and spaces. On my 
barcode, thick is twice the size of thin, but on the real barcode it 
seems to be something like 2.5 or something. (Obviously, you can't 
easily represent this as a sequence of 1s and 0s. But hey, that's the 
Real World for ya...)

I'm almost tempted to see if the reader can actually read my barcode. 
Almost.

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