Method and apparatus for decoding bar code symbols using gradient signals

摘要

A bar code reader decodes a bar code symbol in a pixel image by transforming the data corresponding to the symbol along a first scan line, where the transformation comprises rotation and stretching. The reader generates a whitening gradient vector, a blackening gradient vector, and a count vector from the transformed data. The reader then transforms (by rotating and stretching) another set of data corresponding to the symbol along a second scan line. The reader updates the whitening and blackening gradient vectors and the count vector using the second set of transformed data. The reader then generates whitening and blackening gradient signals from the whitening and blackening gradient vectors and the count vector. The reader segments the whitening and blackening gradient signals and generates a single one-dimensional reconstructed signal based on the weighted centroids of the two segmented gradient signals. The reader then decodes the symbol by decoding the reconstructed signal.