> This one is about bar code scanning. I want to read bar codes
> with a wand type scanner. (Both UPC and code39 would be nice, but
> I can live with UPC only) The problem is, given the wide range and
> fluctuations of the scanning speed, it seems difficult to calculate
> the widths of the bars... Is there a simple method?

I don't have any advice if you want to compute the absolute widths
of the elements.  But I don't think you need that.  You can just
measure the ratios between light and dark and deduce if a bar was
"wide" or "narrow".  From that information, you can decode it.

I'd recommend "Handbook of Bar Coding Systems" by Harry E Burke.
My copy is copyright 1984 by NCR Corporation.  It's published by
Van Nostrand Reinhold.  It's not too thick and used to run ~$50.
An appendix at the back covers a dozen bar code standards.

You might also contact the "code control organizations".  UPC is
UPC Council in Dayton Ohio at 513-435-3870.  Code-39 is Interface
Mechanisms in Lynnwood Washington at 206-743-7036.  Both contacts
are from the vendor list in the above books bibliography.

                                                Lee

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