READING BARCODES USING DIGITAL CAMERAS ... - KULIS

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Abstract: All people go to the supermarket to buy something that needs lots of time. Each product has a label made up of lines with different thicknesses. We go to cashbox when buying these products. Cashiers pass the products through a hand-scanner to see the corresponding price. In this paper, a method is presented for barcode reading with camera which is based on image processing. Normally, the barcode reading process is performed by laser readers, and laser readers are necessary tools for barcode readings. In this paper we present an alternative method for barcode reading directly from camera images. The advantage of the proposed method is that barcodes can be read directly from the line, having product barcodes look upwards facing a camera located above the line, so that it will not be necessary to pick up all individual products to pass them through a laser scanner manually. Thus the proposed approach will provide speed and simplicity. Introduction: Generally, barcodes are symbols shaped in the form of rectangles which consist of thin or thick parallel lines parallel to each other. Barcodes provide means for automatic rapid data input into the computer. Since the last decade, barcodes are being used in many areas such as market products and electronic devices. The lines on barcodes contain the reference number of the product. This information should be recorded in computers to store each product separately for counting company sales and purchase quantities. When reading barcodes on products using some laser scanning device, a signal is generated by the system and is processed in the computer by some software. Then this information is used to determine which product is selected. This process provides rapid and reliable sales opportunities to companies for selling their products. There are very different types of barcodes: EAN, EAN-13, EAN-8, Code 39, Code 93, Code 128, and UPC are well known. UPC and EAN types are most commonly used cases. The UPC numbering system is used in Canada and America, while the EAN 13 numbering system is used in Europe and Turkey [3]. Figure 1: A sample barcode in EAN 13 numbering system 836
Figure 1 shows a sample barcode in the EAN 13 numbering system structure. The black lines on the top of the barcode represent the logic true or ‘1’, and the blanks represent the logic false or ‘0’. The width of the thinnest black line is the reference width. The reference width is presented by a single bit and the largest line width of the barcodes can be four times the reference width at the maximum. In the same way, the width of the thinnest white line has a reference value, and the thickest white line can have a width of four times the reference width at maximum. There are starting and finishing codes equal to 101 values at the beginning and end of the barcode which show the reference widths. There is a longer barcode giving the 01010 value in the center of the barcode and this code lines have reference widths, too. Barcodes are formed in the form of a bit string according to line thickness to analyze a barcode. There are 12 numbers on the barcode and each number is defined by 7 bits. Barcodes also have 3 start, 3 stop and 5 bits in the middle for referencing. As a result the barcodes are defined by 95 bits in total. Barcode values are not obtained directly from these 95 bits long codes. These values will be obtained using barcode numbering schemes. In this paper, the EAN 13 numbering scheme is used to determine the barcode reading process. The methodology to achieve the value of the barcodes using this scheme includes the following structure: 1. Find reference width using start (3); stop (3) and center (5) guard bits. 2. Remove the reference bits (3 start, 3 stop, and 5 center bits) from the barcode code bit string. As a result obtain the 84 bits long barcode information code bit string. 3. Divide the barcode bits into two areas. The first area consists of the first 42 bits, and the second area consists of the last 42 bits. For the first area: 4. Find first the decimal value parity of the barcode. This parity value will be used to determine the order of barcode code readings. The first 42 bits will be read using the encoding table shown in Figure 2b according to the order obtained from the odd-even table shown in Figure 2a. 5. Select seven (7) bit to encode/decode a digit: a. Find the resulting value by searching the respective odd/even column of the left-hand encoding table shown in Figure 2b. b. Go to step 5 if remaining bit count is bigger than zero. For the second area: 6. Select seven (7) bits to encode/decode a digit: a. Find the resulting value by searching the right-hand encoding table shown in figure 2b. b. Go to step 6 if remaining bit count is bigger than zero. 7. Construct the barcode code using the obtained values. Algorithm 1: Barcode encoding algorithm for EAN 13 numbering system. 837
Page 1: Proceedings of 5th International Sy
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READING BARCODES USING DIGITAL CAMERAS ... - KULIS

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