From the readme:
WHAT THIS IS:
This program is a proof of concept for a UPC code reader based which uses the
built in camera in series 60 devices.
- Print out the included test_upc.gif. It will need to be about 6" wide.
- Install and run the included SIS file on your phone.
- Hold the test image about 8 inches away, under bright lighting without
any shadows falling on it
- Make sure the whole barcode is visible and that there is only white space on
the left and right sides
- Hold steady
- If the app crashes (it seems to every 20 seconds, i'm still working on this),
- If you wish scan real UPC codes you will need to buy Nokia's CC-49 Macro Lens
Expansys appears to be a good source of these in a number of countries.
Your mileage may vary. The built in camera can't focus on objects
closer than about 5cm. A regulation sized UPC code won't provide enough
data to decode at that distance.
HOW IT WORKS:
- The program sets up a timer (PeriodicRunner.cpp) to either take a picture
(when the phone is in use) or read an image file (on the simulator) every
so often. Currently this doesn't allow the app to be as responsive as
it could be.
- The timers trigger the userdraw drawing function in BarcrAppview.cpp
- The first several events trigger the program to power the camera on, then
set the lighting and quality modes (normal lighting, high quality), and
then finally to start taking pictures. Every time a picture is completed,
another one is scheduled.
- Once a picture is available, it is run through a processing algorithm
- The processing algorithm only evaluates a 1 pixel band through the middle of
the picture. This is done so that no resizing, or aspect ratio
correction are needed.
- The processing algorithm's first pass determines the average light and dark
values of the image (the two most common values which are more than 20
values apart on a 255 color greyscale range). The average of that value
then becomes the threshhold point.
- The processing algorithm makes its second pass, to locate the guard pattern.
- Starting from x position 0, a counter is incremented while it is finding light
values (those above the threshhold point). Once it hits a dark value,
it keeps going until it finds another light value. It does this to find
an alternating pattern of dark,light,dark of bars that are approximately
the same length. This is the left hand side guard pattern.
- Once the left hand side guard pattern has been identified, the right hand side
pattern is searched for by searching from the right end of the image.
- When the guard patterns are identified, the average bar size is compared
against the number of pixels between the guard patterns to see if
we're likely to have a good match.
- If a good match is found, each digit is iterated on based on approximate start
point, which is calculated from the end of the guard pattern and the bar
- Each digit is read and then compared to known bit patterns. If there is no
exact match for a number, the read is aborted.
- If the whole UPC is read without any errors, the final value is set on the
- The screen update function (called periodically) detects that a final value has
been read, and stops calling the camera functions. It displays the value.