READING BARCODES USING DIGITAL CAMERAS ... - KULIS

a) Odd/Even Parity Table b) Encoding Table
Figure 2: Encoding tables for the EAN 13 numbering system.
As the first decimal number (for instance the first 9 in the barcode shown in Figure 1) shows
the corresponding row of the odd/even parity table and is not encoded in the barcode, it
cannot be extracted by identifying the thickness of vertical lines. In laser scanner systems,
this number is obtained using parity calculation. For simplification, the parity calculation step
is omitted in the proposed system, and both sides of the left-hand encoding approach shown
in Figure 2b is entered into the database and the correct value is determined by comparing
against both (odd and even parity) cases.
Approach:
Our approach contains an edge detection algorithm to obtain barcode borders from images
acquired using a camera, and some threshold mechanism to process images as binary
patterns.
At first, an image that contains the barcode information is acquired using a camera. The
color image contains in fact the full usable information. For faster and simple processing, the
image is converted to grayscale format. Because the acquired image will typically contain an
area larger than the barcode, it is initially required to crop the barcode area as the rest of the
image is unnecessary.
Because only the barcode region is required, the borders of the barcode line coordinates
must be determined. An edge detection algorithm can be used for determining the borders.
Edge detection algorithms can use different kernels. The Canny edge detector provides a
reasonable and successful approach for edge detection [1]. The Canny detector uses two
kernels, one for the vertical edges and one for the horizontal edges. The utilized kernels are
shown in Figure 3. The Canny algorithm provides an optimal edge detector based on a set of
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