20. A system for generating invisible junctions, the system comprising: a processor; a feature extraction unit stored on a memory and executable by the processor, the feature extraction unit having an input and an output for applying a distance transformation to an electronic document to generate a distance transform, for detecting a skeleton in the distance transform, for determining junction points in the skeleton as the invisible junctions, the junction points having a distance transformation value based on the distance transform, for determining a junction size based on the distance transformation value and for producing an invisible junction feature descriptor for each invisible junction, the invisible junction feature descriptor including the junction size, the input of the feature extraction unit coupled to receive the electronic document; and a feature indexing unit stored on the memory and executable by the processor, the feature indexing unit having an input and an output for creating a feature index for the invisible junctions, the input of the feature indexing unit coupled to the output of the feature extraction unit to receive the invisible junction feature descriptors, the output of the feature indexing unit providing the feature index.
21. The system of claim 20 , further comprising a database to store the feature index, the output of the feature indexing unit coupled to the database.