1. A computer-implemented method for retrieving an electronic document using invisible junction features, the method comprising: receiving an image of an input electronic document; extracting, with a processor, an invisible junction feature descriptor from the image; and retrieving, with the processor, information for an output electronic document using the invisible junction feature descriptor and a geometric constraint.
1. A computer-implemented method for retrieving an electronic document using invisible junction features, the method comprising: receiving an image of an input electronic document; extracting, with a processor, an invisible junction feature descriptor from the image; and retrieving, with the processor, information for an output electronic document using the invisible junction feature descriptor and a geometric constraint. 13. The method of claim 1 , wherein the invisible junction features are feature points, the feature points being junctions of an intrinsic skeleton in a blank space of a text document.