Canon copiers
Robert J. Woodhead
trebor at foretune.co.jp
Thu Oct 21 18:58:04 PDT 1993
Paul writes:
>I'd like to know how they put the serial number into the copy.
Most likely by modulating the Least Significant Bit of the color
intensity in some (or all) color-filled areas of the image. A
set of sync-bits, serial number, and some more sync bits. Repeat
every line, shifted by 1 bit, and you'll get a pattern that is
hard to differentiate from the background unless you _know_
what to look for.
I wouldn't be surprised if there isn't a time and date stamp
as well, plus batch # info.
More information about the Testlist
mailing list