[reportlab-users] upc-a barcodes

[Peter]

On Wed, Sep 8, 2010 at 2:37 PM, Steve Romanow <slestak989 at gmail.com> wrote:

>

>> It has been a while since I worked on this, but aren't 12 digit UPC-12

>> barcodes the same thing as a 13 digit EAN barcode with a leading

>> zero added?

>>

>> In a sense, you *have* to look at the length to tell them apart ;)

>

> I think my difficulty with this stems from storage of UPC values with the

> check digit already computed.  Even if I took off the last char, the barcode

> was still shifted one position when using ean.py.  I have moved on to

> another task, but will revisit this in the future.


Again, this is from memory, but isn't the check digit the trailing (right
most) digit? On the other hand, the "extra" leading zero present in
EAN13 barcodes is the left-most digit.

I don't recall the details, but computing the check digit on demand
is pretty easy.

If you are storing 11 digit UPC numbers without the check digit, you
would have to compute and append the missing checkdigit to get a
full 12 digit UPC number, and add the leading zero if you wanted to
turn this into a full 13 digit EAN number. (Or do the reverse if that
is what you meant).

Peter