Methods and apparatus for inferring orientation of lines of text

Abstract

The techniques for determining the orientation of lines in images disclosed herein take as their starting point an apparently universal typesetting convention: that symbols are generally closer to other symbols in the line to which they belong than they are to symbols in other lines. The techniques make a graph by connecting symbols in an image of a block of text with edges (lines) and then determine the predominant orientation of the shortest edges. Because the symbols in a line are closer to each other than to symbols in other lines, the predominant orientation of the shortest edges will be the same as the orientation of the lines. An advantageous mode of obtaining the shortest edges is to construct a Euclidean minimum spanning tree from the graph. A Euclidean minimum spanning tree of a graph contains all the nodes (symbols) of the original graph but connects the nodes with the shortest possible set of edges. The edges which predominate in the Euclidean minimum spanning tree are the shortest edges. Which edges predominate is determined by means of a histogram.

Dependencies are inferred from the claim text.