Yukihiro Shima

An algorithm for the skew normalization of document image

An algorithm to normalize the skew of document images is proposed. The skew angle is detected in two stages. In the first stage, connected regions in an image are extracted and some feature parameters are extracted for each region. In the second stage, the Hough transform is calculated for the parameters, and the angle which gives the minimum of the transform is estimated as the skew angle. In experiments using CCITT standard documents, a detection accuracy of less than 0.1 degrees is obtained for printed documents. When graphical elements are included in the documents in addition to printed characters, the accuracy deteriorates to 0.2 degrees .<<ETX>>

A high-speed algorithm for propagation-type labeling based on block sorting of runs in binary images

A fast algorithm for component labeling of binary images is proposed. Component labeling is an important method for separation of objects in document image understanding, especially in character and picture extraction. The proposed algorithm is based on sorting and tracking of runs and label propagation to the connected runs. Each scan line is partitioned into small segments, i.e. blocks and runs on the scan line are sorted according to the block sequence to speed up tracking of runs. It was ascertained by experiment that the processing time is 16.7 times faster than that of the conventional pixel-based labeling method.<<ETX>>

A contour fill method for alpha-numeric character image generation

A new, high speed method filling in the contours of alpha-numeric characters which produces accurate and correct image patterns is proposed. The method is called the improved edge fill method because it improves on a previously developed edge fill method. It does so by selecting fill pixels from contour lines expressed by Freemans chain code and using combinations for neighboring the codes and accordingly processing time is reduced by about 20% over conventional methods. For binary image contour filling, the method eliminates faults found in conventional edge fill methods, and in consequence the areas inside contour lines are filled in rapidly and correctly. The methods effectiveness is examined in experiments using both Arabic numerals and letters of the Roman alphabet. As a result it is found that this filling method is able to produce correct and accurate image patterns and that it can be applied to alpha-numeric character contour filling.<<ETX>>