Patent Document ID: 8744183
Application ID: 13937118

Base Claim:
1. A computer-implemented method of identifying documents sharing at least one common underlying structure, comprising: detecting, by at least one computer, occurrences of a plurality of predetermined image features in a plurality of document images, wherein at least one of the plurality of predetermined image features is common among instances of a form; indexing, by the at least one computer, the plurality of document images in an image index based on the detected image features; building, by the at least one computer, a graph of connected nodes for the plurality of document images by searching the image index, wherein nodes representing instances of a predefined document type are connected by edges in the graph; and identifying, by the at least one computer, the documents sharing common underlying structures using the graph.

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Claim 4:
4. The method of claim 1 , wherein the plurality of predetermined image features comprises one or more of the following: stable features that are at least partially invariant to one or more of the following: scale, orientation, illumination, contrast, and image quality; line segments detected in the document images; and text phrases recognized in the document images.