[Edinburgh-pm] OT Image Analysis / OCR

Wim Vanderbauwhede wim.vanderbauwhede at gmail.com
Sat Oct 2 03:53:27 PDT 2010

Did you actually try tesseract-ocr ? Is it not good enough?
There is also  http://jocr.sourceforge.net/ . Works fine on scans of
letters etc.


On 1 October 2010 22:39, Murray <perl at minty.org> wrote:
> Hope heretic was fun :)
> I'm at a bit of a loss where to start on this, so any suggestions
> welcome.  It's basically an image processing and OCR problem.
> A while back I got an electricity meter -- it measures the total
> household usage, requires no wiring and can be plugged into a computer
> for fun graphing applications.  I'd highly recommend them.
>    http://www.currentcost.com/ (I have an older model)
> Fwiw, we avg ~10 kWh/day, or roughly about £1/day.
> Then I realised that saving electricity is all well and good, but it's a
> relatively small fraction of our energy usage.  Gas being the big
> elephant in the room (mainly for heating).
> So I'd like to measure our gas usage, daily or preferably hourly.
> Unless someone knows of a no-hassle, no-pipework gas monitor, I hit upon
> the wheeze of getting a cheap webcam [1] and placing it in front of the
> gas meter and capturing an image.  Here are a couple of test samples:
>    http://minty.org/gas/a.png
>    http://minty.org/gas/b.png
> I've cropped the pictures to show just the meter.
> Basically the problem is how do I convert those into "6500" or better
> "6500.96".  Bonus marks for additionally converting the red arrow/dial
> (although I suspect that might actually be easier).
> The best I've found so far open source ocr is
> http://code.google.com/p/tesseract-ocr/
> I'm not entirely against just running a brute force approach in
> Perl using known tiles and looking for "fuzzy" but likely matches.
> But I'm wondering if anyone has a smarter idea?
> Some points of note:
> - I can "fix" the camera, but as the cupboard is used periodically for
>  storage, there is always a chance of a small knock.  It'd be best to
>  assume the camera position will move a small amount over time, but can
>  be (roughly) hand-calibrated easily enough.
> - The meter has a glass front, causing horribly lens glare if the camera
>  & it's led lights are placed straight on.  Thus, the image is slightly
>  skewed due to the camera being off-center.  I could go up/down, left
>  or right.  It's in a dark cupboard with no other constant light source.
> - Between the "65" and the "00" is a chip in the glass.  For this
>  reason, positioning the camera to the left works better than to the
>  right.  Similarly, I'd imaging down would work better than up.
> - Worst case is automatic daily image capture and a yearly manual job of
>  running through 365 images and re-keying the meter reading.  But
>  hourly would be a lot more fun, and that is probably beyond my
>  re-keying capacity.
> Taking a weekly reading by hand and averaging over 7 days would be a
> decent approximation.  However I'd like to log temperature too.  I can
> get a close outside temp from the BBC [2] and the CurrentCost device
> logs the room temp.  So a weekly average would loose a good amount of
> fidelity.
> Suggestions?
> [1] http://amzn.to/9OrpWW and I can confirm it works flawlessly on
> ubuntu and mac os x without needing any drivers.  Truely plug n play.
> Only downside is you can't control the leds (or focus, or position) via
> the computer, but hey, they're leds, so we can leave them on all the
> time.
> A pending task is to measure the power consumption of the computer when
> idle with the camera plugged in and leds on, vs camera unplugged.
> [2] http://backstage.bbc.co.uk/data/WeatherFeeds?v=151i
> _______________________________________________
> Edinburgh-pm mailing list
> Edinburgh-pm at pm.org
> http://mail.pm.org/mailman/listinfo/edinburgh-pm

If it's pointless, what's the point?
If there is a point to it, what's the point?
(Tibor Fischer, "The Thought Gang")

More information about the Edinburgh-pm mailing list