Re: iSight barcode scanner
Re: iSight barcode scanner
- Subject: Re: iSight barcode scanner
- From: Cameron Hayne <email@hidden>
- Date: Tue, 16 Aug 2005 18:34:48 -0400
On 16-Aug-05, at 6:17 PM, Sherm Pendley wrote:
On Aug 16, 2005, at 5:11 PM, Jack wrote:
I have started an open source barcode scanner using a firewire
camera based
on the Apple sample SGDataProc code. At the moment is scans UPCs
and EANs
using the iSight well. However it seems it's unable to scan using
other
firewire cameras. (As I don't have one I can't debug it.)
I have a Sony DCR-TRV11 camcorder - MiniDV w/Firewire. I downloaded
and built the sample app, and successfully scanned the codes from a
few books I had within reach.
It was finicky on my old single G4/500 - I had to position the book
just so, and hold it very still for the code to scan. If I were
going to scan a lot of books (or whatever), I'd have to use a
tripod or something and point the camera at a stable surface,
instead of simply holding stuff up in front of the camera
Here's a highly relevant excerpt from an interview with Wil Shipley,
programmer of "Delicious Library":
( http://www.drunkenblog.com/drunkenblog-archives/000581.html )
One trick is to notice that every digit in a barcode is two black
stripes and two white stripes, so if you've read black-white-black-
white you know you have a digit, no matter how quickly it
happened. (If it happened too quickly, you can decide you're
reading garbage and just bail.)
...
In the case of reading bar codes, you don't care if you read
garbage a thousand times a second. It doesn't hurt you. If you
write an algorithm that looks for barcodes everywhere in the
image, even in the sky or in a face or a cup of coffee, it's not
going to hurt anything. Eventually the user will hold up a valid
barcode, it'll read it, the checksum will verify, and you're in
business.
And the barcode recognizer doesn't have to understand every
conceivable way a barcode can be screwed up. If the lighting is
totally wrong, or the barcode is moving, the user has to take
conscious action and, like, tilt the book differently or hold it
still. But this kind of feedback is immediately evident, and it's
totally natural.
Because I can try 1,000 times a second, I can give immediate
feedback on whether I have a good enough image or not, so the user
doesn't, like, take a picture, hold her breath for four seconds,
have the software go "WRONG," try adjusting the book, take another
picture, hold her breath...
--
Cameron Hayne
email@hidden
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