Boundary feature extraction from gray-scale document images

A novel method is presented for extracting closed boundaries of document components such as characters and symbols directly from gray-scale document images based on the surface data structures along with structural features. The method is based on the simple model assuming that a closed boundary of document components can be approximated as a series of horizontal line segments and can be extracted by linking surface components with steep gradients which share commonly intersecting horizontal planes. The proposed algorithm is compared with some binarization algorithms, shown to be effective for improving recognition accuracy for very poor quality data.