Reading And Recognition Technology Of PDF417 2-D Barcode

The barcode technology has been developing rapidly since 20th century and the barcode has been used in various application fields. In the modern life, One-dimensional barcode can no longer meet the needs in several aspects such as transportation, capacity and expressing. But the appearance of two-dimensional barcode solves these problems. At the same time, the two-dimensional barcode adopts the advanced RS error correction code, which improves the read capability of barcode.This research is about the PDF417 barcode which is a representative stacked barcode among the two-dimensional barcode. We use ordinary camera to capture the barcode image and design the correlative recognition and decoding algorithm. The content of this paper is as follows:Firstly, the research studies the encoding rule of the PDF417 barcode and the encoding algorithm. Next, the coding and decoding principle of Reed-Solomon error-correcting code (RS code) is briefly introduced.And then, the paper gives the pre-processing of the barcode image. The average step of the processing is as follow: filter the noise of the barcode image, get the binary image and calibration the barcode image to horizontal position. Because we use ordinary camera to capture the barcode image, the edge of the barcode image is very vague, and the image always has some kind of distortion. If we use the general binarization method, the effectiveness and efficiency can not meet the requirement of the experiment. In this paper, we improve global threshold method to binarize the barcode image, compare to the general global threshold method and Otsu method, not only it can achieve reasonable results, but also the time complexity of the algorithms is adapt to the real-time in PDF417 bar code recognition.At last, the Recognition and decoding process have been analyzed and studied in detail. The traditional methods are mostly based on the edge of barcode image and the unit of the code word module. The first method has high requirement in barcode quality and the second method require high accuracy of the image Acquisition Facility. When there are some pseudo-edges in the barcode image or the barcode image has some kind of distortion, these methods are difficult to get the right bar code information, because all of these above, we usually use RS error correction code to correct error information, but even RS error correction code has its own shortcoming. So based on the research of other people's work, a new algorithm has been put forward to avoid the over-reliance of error correction code. In this paper, we first calculate the width of barcode unit, and then use it to detect all of the start point and end point from the original barcode image, Thereby positioning the symbol character of barcode image. The algorithm this article taken has high accuracy and low-sensitivity to both barcode quality and image Acquisition Facility, in the same experimental condition, can extract the 2-D barcode accurately.