A PDF417 2D barcode image decoder with new perspective correction method using line correspondence is designed and implemented under an industrial vision development platform. The decoder is implemented as a ready-to-use and international standard ISO/IEC 15438 compliant system. In this study, we proposed a method for perspective correction, in which line correspondence is used to achieve higher performance than that of point correspondence. Characteristic in barcode decoding is used for reducing computational complexity during correction: 1. Barcodes are rectangular; 2. Aspect ratio of a barcode usually does not affect decoding and results. The characteristics provides four sets of line correspondences at boundaries of the symbol before and after perspective correction. By this correspondence, an optimal perspective distortion transformation matrix can be estimated. Hence, the restoration or the reverse transformation can be conducted for perspective correction. In our method, a more accurate method of using line correspondence is used. This 2D PDF417 decoder provides a calibrationless, accurate, and automatic method for perspective correction.
