Image Prepocessing Algorithm Study On Pdf417 Barcode-image Information Abstracting Based On Characteristics

Although one-dimension barcode finding its widely application, it is only an encoder of the goods due to its limited information-capacity. One-dimension barcode can't involve the more information for describing its feature in text mode, and it dose not work where the database and network aren't available. Two-dimension barcode is just invented to supplement this defect. There are many standards of Two-dimension barcode, and PDF417 standard is the most popular one, which has been published as China national standard.For the technology of reading 2-dimention barcode is image-based, image processing technology adopted in PDF417- barcode processing is the foundation for the application of the barcode. Barcode-processing of image-based is the course of two steps: the processing of the image obtained by video-camera or scanner with certain kind of algorithm and decoding. The study in this paper focused on the pre-processing algorithm of PDF417-barcode.Due to the inevitable noise introduced when obtaining the image, the non-uniform illumination, barcode contaminating, and geometry distortion caused by camera-lens, it is necessary to pre-process the barcode-image in application case. In this thesis, the noise-ellimination and the binaryzation of barcode-image are discussed with general algorithms existed in the textbook in the field of image-processing. The effects from applying different image-proceesing algorithms for barcode-image are compared, e.g. we studied some noise-filtering, image-rotating and image-binarization algorithms with different algorithms and different parameters.The main jobs of this paper are to study the measuring principle of image-skew of barcode based on the base-line characteristic of the barcode-image and to provide the algorithm for rotating the image. Extracting method of valid barcode region is also under discussed. Furthermore, preliminary analysis of contaminated barcode-image recovering technology based on the characteristic of PDF417 barcode is also studied.All algorithms studied in the paper are simulated and verified on MATLAB6.5 platform, and the results are satisfactory. The works can be the foundation of developing a better barcode-image reader for PDF417 application system.