iPhone Barcode Readers

[Piers Cawley]

On Tue, Mar 1, 2011 at 11:15 AM, Kieren Diment <diment at gmail.com> wrote:
>
> On 01/03/2011, at 10:05 PM, Christopher Jones wrote:
>
>> On 1 March 2011 09:49, Dave Cross <dave at dave.org.uk> wrote:
>>>
>>> Need some advice on iPhone Barcode reading apps - so I turn to london.pm, my
>>> favourite group of iGeeks.
>>>
>>> My wife is a teacher and they're about to start a stocktake of all of the
>>> books in the English department. Rather than count them all, she wondered if
>>> there was an iPhone app that could help them.
>>
>>
>> I'm fascinated to know how you could use an iPhone to scan a barcode - can someone explain?
>
> With the camera ;)  Scanning high contrast images for information is a reasonably well solved problem.  Get rid of noise and highlight edges with a LoG (laplacian of gaussian filter - could be wrong here my knowledge is ancient and theoretical), then seeing as a barcode is basically a 2d image, use the barcode spec to get the information out of it by walking along the line measuring the thickness of the bars.

There's a rather nice worked example of implementing barcode scanning
in 'Real World Haskell'.