METHOD AND APPARATUS OF REMOVING SUPERIMPOSED LINES AND RESTORING PIXEL VALUES IN IMAGES CONTAINING RECURRING PATTERNS

摘要

The invention is a method and apparatus to restore the obscured poriton of an image of a sequence of characters or other patterns in the presence of superimposed lines. The character restoration is accomplished by means of two kinds of statistical information, the frequency of occurrence of image pixel value observations on either side of the obscuring line and the frequency of occurrence of character slice transitions within the width of the obscuring line. This statistical information is organized as a Hidden Markov Model. Having estimated the model's probabilities, the Viterbi algorithm is then employed to determine the optimal restoration across the length of the line. Two tasks are performed prior to the character restoration. First the Hidden Markov Model is trained. This task involves scanning across sequences of characters to estimate both observation and tansition probabilities. Model construction is done off-line and typically only once. Prior to the run-time character restoration, the line itself is located using a modified version of the Hough transform. Local eigenfits are employed to reduce the necessary computation.